For the diff- I believe I will need right around 1 quart. But will I need a low profile 14mm hex socket.
For the MT in general- any special sized sockets?
For both- what is your method to jack this thing level safely? Can you lift from any single point in the rear?
On an e30, I have no idea. On the e46...I'd suggest you read threads on jacking safely...
But for me, being 'not huge' I just drive on my 2.25 inch high ramps (home built and I have four)...and do it from there...no jacking involved and perfectly level.
You could jack from front center or rear center jack points and then put on jack stands (make sure you chock appropriate tires!)...if you jack in the back, your car will tend to roll forward a bit...so I start with car in gear, chocked in back and jack up front first...lower to jack stands...go to back...then back front (so I don't have one end substantially higher than the other...I'll do it in a couple of lifts when I need more room. But, being a former spelunker in my youth, don't mind tight places!
Stack two 2x10s/12s together...cut 45 degree angle on them...voila...homemade ramps...(I've got photos of mine somewhere around here)
Or, the best would be the 80 ton custom jack stands a guy in London made out of mdf...just search 'jack stands'!
Doug