The reason that you have received no replies is probably because the vast majority of the attendees on this site are in the US. In the US people primarily drive automatic transmission cars. I am one of the very few exceptions on this site.
For this reason MB brings VERY few manual transmission models to the US. I have an '88 300E with a manual. There were only 300 or so brought to the US that year.
Anyway to your project. I have never done a clutch in your particular model, but I have done clutch jobs on a number of other similar models. There are really no tricks to it, but your questions do bring up a few points.
The driveshaft is a little different situation than many or most other cars. There is a large nut in the front section that must be loosened to allow the driveshaft to collapse. It will collapse barely enough to move out of the way once the flex disc bolts are removed. Mark the driveshaft in front of and behind the big nut so that if the splines were to slip apart, you will be able to put it back in its original relationship so that you don't upset it's balance.
Also mark the position of the driveshaft at the transmission so that it goes back in the same position related to the companion flange at the rear of the transmission.
Do not disconnect the slave cylinder from it's hydraulic line. Just unbolt it from the bellhousing and swing it out of the way.
I'm sorry I can't help you much with the rear main seal. I'm not sure if yours is a two piece or one piece seal. If it is a two piece and indeed it is leaking, I expect that the pan will have to come off to replace it. If it IS leaking, I would expect that you would be seeing oil puddles underneath.
Good luck and let us know if we can provide any more help.
Have a great day,