Hmm the previous link I posted was for the output flanges; this is the input flange I realise now... (I already had problems placing that nut...)
For the input flange you have to mark up the nut with a centerpunch or a marker. Afterwards you tighten the nut to the same postition (count the turns obviously)
There is no torque setting, as this probably effects the gear alignment from the pinion/spurgear setup.
If you've already released the nut....you're screwed (well, you have to set the backlash again for the gears, and then you'll need some inside information regarding the backlash data on the gears themselves).
This is the correct TIS link:
http://bmw.workshop-manuals.com/Z_Se...ex.php?id=1063
It's 5 pages long so you have to click next page a few times.
You have the 210 diff with lock (only important for the special bmw tools).
You have to get the flange off with a puller after you've removed the nut (that can be fun
)
Shaft seal is indeed 33121213949
Lube the seal a bit prior to installation.
With the nut sits a securing/retaining plate 33121205138 accoring to TIS/realoem
You'd probably need that too.