A few tips in no particular order:

M50 and M52 have two different oil pans. The pan that you use depends on the intake manifold you decide to use. The dipstick is larger on the M52 as it ties into a oil/air seperation system that's part of the intake.

Early M52s have a crank trigger wheel, later ones do not. If you have a later M52, you'll have to swap balancers with the M50. Be sure to get a new bolt and torque to spec.

You'll need to swap over all the OBD1 M50 sensors to the M52. Crank pickup, cam pickup, knock sensors. M52 temp sensor unit can be used if you splice a M52 connector into the M50 harness. Early M52s have enough ports on the cylinder head to swap over both the M50 temp sensors

You'll need a coolant pipe adapter fitting from active autowerks. Make sure you use locktite when installing.

M52 uses a different power steering pump. You'll need one of those and a M52 specific high pressure power steering line.

Tuning.. I'm just using a 1995 M3 chip right now. Seems to be OK.

Those are the highlights! If I think of anything else, I'll send it.