Well I just finished, after speaking to my local MB service advisor and hearing "No parts" and $900. I was off to tackle it.
My local car wash "gorillas hand ajusted the inside rear view mirror and the clips broke, mirror was loose in housing.
I would suggest removing the lenses on the overhead lights in the switch panel there are two screws behind the bulbs and the whole panel comes out. Pull the cover off in front of the mirror and disconnect the connector. Insert a screw driver between the two aluminum panels and the mirror mount will release. It is held by two spring loaded plungers on each side. The front and rear covers are held by a ridge at the bottom and 4 catches at the top. I would start at the bottom (nothing to break). The mirror is held to the adjusting mechanism by two leaf springs that hold it to the front frame. Both of mine at the top were broken off. These leaf springs have a little bend at each end, I found the smallest drill 1/16 or less and a self tapping screw and drilled a hole in the bent end. There is not a lot of material to work with but doable. I took a little tension off the two springs for my own comfort. I then drilled a small hole in the plastic where the tab had broken off ( 1/4in I immagine, use the spring hole for reference Then started the screw in the hole after tapping the leaf spring it with the screw first, the drill hole should be in the middle web, use a flat head screw and countersink or not. Then assemble, tightening the screw or screws. I did not put on the rear cover but could have, hook at top snap in at bottom, push assembly into frame I oiled plungers. Plug in connector, install lights, and replace cover. Then I would open a "cold one" and amire your work. I did it in the sun in the parking lot and needed one.
If the other two tabs break i will do it again, this time i wiil shop for screws and will tap the bracket
Peter, although I admire your work and your posting, you know better than to let someone else touch your W140. My wife brother-in-law hand adjusted the rearview mirror on my 140 once (what the hell was I thinking when I let someone else drive her, I don't know) and the gears/motor in it made a grinding sound for a second or so, but then miraculously, it has worked since then. Well, I have never let anyone sit in the pilot's position since, and so the question to change the position of the mirrors, seats, or anything else has never arised since then. Problem solved.