welcome to bimmerwerkz. firstly look in the classified for parts for sale.
secondly yes you can put an m3 engine in your car, there is a bit of work that is required to make it all work. (do a search on it)
as for the window i have a feeling you might have something stuck in the track. if your mechanically incline try pulling the door skin off and check the track. (also do a search as this has been done and fixed by quite a few of us)