I wouldn't worry so much about the BB, but I have worked on some cheap cranks that are simply too crude and badly made to bother with. Incredibly soft metal, easily stripped threads, etc. I can imagine your "Lasco" crank might fit into that category.

For $20 you can get a quality (albeit cheap) Shimano compact square taper crank, brand new: http://www.ebay.com/itm/NEW-SHIMANO-...item35eaa126bc

A new Shimano bottom bracket should run you another $10-15.