Like he said, it's a learning experience. It is a lot more nerve wracking to try out new things on a frame you paid $300+ for.

The BB you need depends upon the crankset that you end up using. Those cottered crank spindles were pretty long, you'll need a newer square taper that will be much shorter. This may be a case where you'll have to try out a couple different BBs to find on that gives you the chainline you want.