I got the parts today and decided to put the heater in right away instead of leaving things until winter when it's 30 below, like I usually do. The hardest part of this fix was disconnecting the adblue output hose as it left the protective housing. This is located in front of the tank and you will find it as you look from under the car. This was tricky getting off. Disconnect the electrical pushing out the grey tab then pushing the tab into the fixture to get it over the inner ridge. This will apply to all of the electrical fixtures. Then disconnect the adblue connection. Put a flat screwdriver between the connection and gently pry apart.
There are four nuts that hold on the dust cover as well as four bolts that attach the cover to the bumper. They are 10 mm and easy to take off. Once the bolts are off the cover will come down not off. This is all it needs to do.
Disconnect the two electrical connections from the tank. They are held on by slides. Slide the bottom connection down and the top across to remove from the tank and then disconnect. They are also held to the side of the tank which is simple to remove.
There are two nuts to remove to take off the holding straps. Follow the straps to the rear of the tank and you will see the 13mm nuts. Once the straps are off the tank will drop down and out.
Take a picture of the top of the tank and disconnect all of the electrical fittings.
Remove the pump by taking off the three hex nuts and set aside.
Unscrew the top ring. Mine was pretty tight but came off with no tools needed.
Take off the top of the heater by placing a flat screwdriver between the seal and the top and pry up. At this point once the top was off I cut the inner cable and hose as I had a new part and it exposed the inside of the tank. Remove the inner rubber seal and turn the inner heater counter clockwise to release the heater from the tank.
The adblue heater I purchased from Exoparts had a new heater, rubber inner ring, outer top ring, new hex nuts for the pump, new rubber rings for the under side of the pump and new zip ties which I used. There were some other plastic fitting which I had no idea what they were as I did not see any of those parts.
Putting the heater into the tank in the groves, turn clockwise to lock it in. Put in the inner rubber ring. Place the top of the tank on the ring. My top had an arrow which matched an arrow on the tank.
Put on the outer ring, tighten. Put on the rubber o-rings onto the bottom of the pump and put the pump onto the heater with the new hex screws. Put on the zip ties onto the outer ring in the same places as the original, attach the electrical cables and connect them. Refer to your picture.
New heater is in the tank put the tank in the car and connect all fittings. Put on dust cover and connect to external adblue hose. Done.