Just finished 10 minutes ago...
...on a 126, probably similar. Followed the CD, fuzzy but the parts helped to explain themselves. My model used 2 different regulators, so I had to remove door liner to order the right one. On disassembly of the unit to install, I could see that mine failed because one of the rubber grommets that should space the motor bracket had not been installed at some time prior, causing regulator to move slightly sideways. Only snag I ran into was removing sliding jaw from rail, but if I had removed all three retaining nuts from regulator/motor assembly before disengaging rail the whole unit would have easily slid forward. My greatest fear before starting was how to wedge the window up so it wouldn't fall while I was working. Two pieces of cardboard in the tracks turned out to be enough, but I would have been more comfortable using 2 small rubber wedges, just couldn't see anything in the garage to make them with. Pay close attention to position of regulator teeth in relation to motor so they install in the right position for travel. Would have finished in 90 minutes, but with only two hands, it took an extra 45 minutes to get the door liner back on right. An extra person to hold in at the correct spots would help there. If you've never taken a door liner off, study it a little on the CD and read here first, MB does not use push fit retainers, it's a clip system that disengages when you lift up on the liner. Very nice, but takes coordination to reinstall. All in all, a smoother job than I anticipated. Good luck.
'02 C230 Kompressor
'89 560 SEL "Frau BlueCar" (retired April 2004)