To do it right plan on about $2000. You will need E30 M3 parts for almost all of the conversion. You need front bearing with hub flange, new rear wheel bearing because the stock one gets destroyed taking the 4 lug flange off, new 5 lug flanges for the rear, new axle nuts front and back, front axle nut dust covers, complete E30 M3 brakes (discs, pads, calipers, caliper brackets, wear sensors and mounting hardware. It also helps to use the E30 M3 strut housings. You are also going to need to find 5 lug wheels. The easiest and most cost effective way to go is use stock E38 740iL 16x8 basket weaves.
Why are you wanting to do the swap?