Just a couple of comments,
If you are only replacing pads, you can remove the caliper without removing the carrier, the 2 metric 18mm bolts that you mentioned will remove the carrier along with the caliper. The disadvantage of doing that is that it is heavier than the caliper by itself and it is harder to tie down out of the way, the 2nd disadvantage is that you don't get a chance to inspect and re-lube the pins on the caliper.
I recommend that you first compress the caliper piston with a C clamp before you remove anything (and after you loosen the reservoir cap), then you use an allen wrench to remove the caliper, pull out the pins, if they are corroded, polish to a mirror finish, relube and re install, replace the pads and reinstall the caliper on the carrier/rotor.
Well, I started on the front brakes this weekend (E500 2004) and ran into some problems.
I removed the 18mm two bolts and removed the caliper. But the brake pads don't simply come off. The pads seem to have the metal pin running through the tabs on the brake pads. I looks like I need to remove the two Torx bolts from the side of the caliper to get the pads off. These are not allen bolts, but Torx. I tried my T-40 bit, but is was too small. So I probably need a T-45??
So, given that my car is and E500 and not and E320:
1. Do I need to remove the Torx bolts and side plate to the caliper in order to remove the pads? Again, there is a pin that runs through the tabs on each pad.
2. Does anyone know the exact size of the needed T-Bit / Torx bit? T-40 is too small.
As the guy above indicates, it appears as if I don't need to remove the full caliper / 18mm bolts in order to replace the pads. Just the Torx bolts. We will see... Given how hard is was to break the 18mm's loose, they may have never been removed, and I have 102k miles!