Procedure : Inspection, Preparation
Step One: Check wiper transmission for problems.
With the motor taken off you should be able to move the wiper transmission around, see how it operates, note the linkage, movement and contact points, and check for problems. Mine was surprisingly stiff, but I have nothing to base this on, so it could have been normal. Take this time to take your motor apart to learn ya somethin'. Below is my motor taken apart, on the zoomed in image you can see where the worm gear was damaged. This then destroyed the plastic gear. MB engineers used the position of the plastic gear to detect the parked position, and not the position of the internal motor. This plastic gear's position directly relates to wiper position, so this problem won't cause your wiper to park in an odd place. The motor will keep running without parking unless it doesn't detect the park position for a given period of time. Then it will stop the motor anyway. So your wiper may stop in an odd place while the motor continues humming away. After a certain amount of time has elapsed the motor will just shut off. My gear was in good enough shape that I could actually move the wiper by hand in the places it got stuck to get it back to park.
Step Two: Clean wiper transmission linkages.
Use break parts cleaner and get the old grease off that likely has grit packed in with it. Clean all the contacting points and surfaces thoroughly. This isn't your normal "lube job" on the wiper system. It could have failed due to problems in the movement. Give yourself peace of mind and spend the time to clean this well.
Step Three: Lube all contacting parts on wiper transmission.
You can not see the moving parts inside part of the transmission. There's a small gear that rides inside a reverse gear as the wiper moves from side to side. This small gear being turned is what moves the elbow that is underneath and attached to the main post at its base. This creates the "M" motion the wiper makes. There are three holes you need to line up to be able to spray some white lithium down in there. If you get the post into the vertical position these should line up. Get your straw in there and spray away. Make sure you aim your straw around. Then spray all the visible moving parts. Move everything by hand and repeat your lubing as you see fit.
Step Four: Park new motor by itself, UNATTACHED!!!
Make sure the car is off. Replace the fuse and plug in the motor. Have a helper hold it or get it secured somehow. Get in the car and turn it on, but don't start it. Run your wiper on intermittent and check that the motor runs, stops, runs, stops... etc. Put your wipers on slow, and check the speed and sound of the motor, remember the sound for later testing. Then put them on high and check again. Hit the sprayers to see if the motor comes on for a moment and shuts back off. Finally, run them on slow for a bit and then turn them off. Let it come to rest naturally, remove the key, unplug the motor and remove the fuse. You have parked the motor and are now ready to begin installation. You're more than halfway there.
Procedure : Installation (not reverse of removal, exactly)
Step One: Attach new wiper motor to wiper transmission.
Position the motor and install the three bolts that attach it to the transmission. Your motor has been parked in the starting position, but now you need to set your transmission into the parked position before pressing the transmission's main arm onto the motor shaft. Since the motor spins constantly in the same direction and it is your transmission that makes your wiper move back and forth, you can choose to start your wiper in whatever position you like such as on the passenger side, up the center, or maybe at a 15.67 degree angle, whatever you like. To return it to "factory" settings there is an alignment mark on your transmission linkage to show you how everything lines up. That mark (or just a little bit of common sense) will show you exactly how to position everything before putting it back on the motor. I wouldn't worry about it being perfect. In fact, where I placed mine the arm wasn't straight with the alignment mark. Press the arm on and tighten the nut on the shaft. As you tighten you might get beyond the motor's internal friction point and begin turning it. This is where your 13mm open end wrench comes in handy because the socket will eventually get in the way of the linkage. I'd also advise getting the motor back into the parked position before plugging it in or it will start moving as soon as you turn the car on. Use your wrench to keep turning it in the same direction until it's back to the alignment mark. Don't try to go backwards, you'll just loosen the nut! You could also damage the motor and you'll be doing this replacement again in 18 months!
Step Two: Install wiper motor and wiper transmission as one unit.
"Roll" the assembly into the damper bushing with the bolt, then let the other damper bushing (the one attached to the assembly) rest in the white clip, then align the bolt holes over the bolts on either side. Get the flange seated well in the damper bushing before tightening the bolt about 1/4 of a turn. DO NOT OVERTIGHTEN. This is not a traditional bolt. It merely turns on a plastic ramp. This is merely intended to absorb vibration. Clamp the white clip over the other damper bushing. I used my pliers on the wide setting and made sure they were clamping down on the very top. I could not get the clip to close completely by hand, it wouldn't click all the way in and was easy to flip back off. Once the clip is on right it should take a decent amount of effort to get it off by hand. The problem is you have to compress that bushing, and it's a bit tough to do by hand. Now put the two nuts back on and proceed.
Step Three: Plug-in motor and install motor fuse.
Your new motor should have a rubber grommet floating down the wire, there should also be a similar rubber split-grommet on the vehicle. Route the wire through the one on the vehicle and install the one on the wire in the side wall of the fuse panel. Pay attention to the shape, it is molded to fit in one direction only. Pull most of the wire back out of the box through the grommet to make it easier to close later. Clip the motor power cord in, then plug in the fuse and get ready to test.
Step Four: Test motor operation.
Get in your car and test. With everything bolted down not much can go wrong. Your wiper can not extend too far one way or another, Mercedes' engineers are just that thoughtful. It also can't go too far to one side or the other. This test gives you a chance to see that it stops in the right place. You will also want to pay attention to the motor sound and compare it to your earlier test. Now's the last chance you'll get to see if the motor is straining due to a faulty transmission. I also used this opportunity to add lube while everything was in continuous motion. Hopefully you haven't gotten overzealous and installed your wiper - if you have and you're testing with a dry windshield then you are putting your motor at great risk.
Step Five: Install primary and secondary fuse box covers.
If the test was good, turn off your wiper and the car, then remove fuse 44 for safety. Put the secondary cover on, screw it in, and then place the primary cover back on.
Step Six: Install fresh air ventilation duct.
This is the big piece, but remember, the shroud under the wiper transmission needs to go on first since 2-3 screws mount through it. Slide the shroud into place, then finagle the duct into position. Install the plastic nuts on either end, don't over tighten (they are plastic...) and then install the 10 screws. You may have to play with the alignment on each screw to get them in so don't tighten any of them all the way in before getting all of them started. After the nuts and screws are in place, clip all the clips on.
Step Seven: Install driver and passenger ventilation intake registers.
When you removed these all you thought about were the three clips, but flip them over and look on the back and you will notice that they have clips there that slide underneath the plastic over the windshield. Get it all lined up together as you slide all the clips in at the same time.
Step Eight: Attach wiper transmission cover.
It clips over it with the rod going through the hole at the end. That's it.
Step Nine: Attach wiper arm.
Remove the 5mm hex head bolt. Slide the arm over the post, and then install the bolt back where it goes. Tighten that down. Again, keep in mind this thing is spring loaded and it'll take a little pushing to get it on right. Attach the wiper blade.
Step Ten: Wet your windshield and test.
Oh... reinstall fuse 44, first. You're done. Clean up, put away your tools and take her for a test drive.
You can simply remove the wiper blade and arm and then that plastic cover to periodically lube it up again. If you run your wiper and try to stop it in the middle you can even lube the inner gears. Take the vents off again if you feel like lubing the linkages in the back.
If you have any troubles I've subscribed to this post. I encourage you to ask questions here, not through PM. The whole point of a board is to share your knowledge. I created this post because all of the others were lacking in one area or another and people kept "+1"ing a post that was 3 years old. Hopefully this covers it... it IS long enough, don't ya think?!