[MPWR]

The oil filter housing leak is very common on the M44, and the DIY fix is pretty straightforward- a new gasket should do the trick. There's a writeup on how to do it in the garage section.

The starter motor is hard to change on all E36s. I haven't done it on an M44, but often you have to remove the intake manifold. I think Pelican has an online writeup on their site- it's also covered in their 101 projects book.

Belts on an M44 could not really be easier. Remove the intake trunk and radiator fan to give yourself some room. The main drive belt has an idler wheel and a tensioner (they look the same), by the alternator. The tensioner is the lower one. Pry off the plastic front cover with a screwdriver, and a breaker bar with a 16mm socket will release the tension. The a/c pulley has one tensioner also, and I believe you need a hex head (maybe 7 or 8mm) on a breaker bar to release it.