Jobs like this REALLY need an impact gun
Even those cheap Princess Auto $50 electric ones will do.
As for a lock tool, you just need a piece of 1/8" steel (or aluminum) about 6" long x 1" wide. Drill 2 holes, 1 on each end. Put in 1 pressure plate bolt in one hole, and attch to the flywheel. Put in one of the tranny mount bolts in the otehr hole, and attch to the engine. This will stop the thing from rotaing when you need to retorque the bolts (GET NEW BOLTS when you put it back!!!)
There is a really good write-up on this at: http://www.pelicanparts.com/bmw/tech...ch_Replace.htm
Has tonnes of pictures!