That is a awsome deal for that car. I have a 98 318ti and I love it. As for a girls car not really not any more girly than a civic,cavalier, neon, or corsica. If you think it looks like a girls car, put on some lowering springs, a carbon fiber hood, tint the windows, and get rims.
Also another alternative to an engine swap is the downing atlanta supercharger kit or the mossleman turbo kit. Really compared to most 4 cylinders 138HP is pretty decent out of a 1.9L and they get about 35MPG on the highway.
As for being easy to work on, I would say that the M44 engine is pretty simple (if you can fix a GM you can work on a BMW).
My current project is finding or getting my cams reground.