I replaced the Rubber Support Mount in the trunk this morning. The $230 price for the part through my local Mercedes dealer was a hit but it was comparable to what I could find online. The old mount was a disaster. This wasn't visually evident prior to removing the old mount because the it was collapsed and the steel "washer" otop was flush against the top of the mount frame. I haven't driven it yet but there's no way this could be anything other than a huge improvement.
I had no assistance doing this and I thought it would be beneficial to share a few notes on the removal/install.
Removal was straightforward - loosened and removed the large center bolt first, then loosened and removed the four 17mm bracket bolts. I did have to pry the bracket up away from the frame but it was done rather easily and the entire mount then was pulled free.
Installation was a bit more challenging because the arm off of the differential that bolts to the new mount was not in center, nor perfectly vertical. I was not able to improve its alignment by jacking on points on the differential to try to change its position. So I slipped the new mount over the top of the arm as best as it would go (which was just barely). I then used a large round punch through the new bracket and into the threaded hole in the arm (where the large bolt will go) to leverage the arm into a position where the new mount could be lowered into position. Surprisingly (and thankfully) this didn't require a lot of force because it wasn't too far out of position. With the mount down, I used the same punch in the frame holes to align them with the bolt holts. I pulled it into position where I could install one bolt, ran it down as far as it would go without compressing the lock washer, then repeated this for two more holes (progressively easier to do). With three bolts installed, the fourth went in easily. I then torqued the four bolts in the frame to 32 ft-lbs, installed the large "washer" being careful to align the notch with the boss on the arm, and tightened the large center bolt to78 ft-lbs.
I took a photo of the old mount but suffice it to say that it would be obvious to a casual observer that it was junk at this point.