krapes

So my left crankarm has been coming loose. I looked up the problem and decided that I probably needed a new crankarm (rounded taper in the arm), but since I was already buying stuff- I also decided to go ahead with a whole new crankset with 165 mm length cranks and a larger chainring. I ride fixed gear.

Here come the questions: 1.) Should I consider changing out the bottom bracket also? 2.) I remember reading a debate somewhere about whether to tighten the bolt on a new crankarm to a specific torque or whether to just tighten it as much as possible. I'm sure my crankarm came loose because of lousy installation on the part of the idiots at my LBS. What should I do to ensure that I don't have this problem again? 3.) Is there anything else I should be considering here? I'm kind of nervous as changing the crankset seems to be basically like an engine swap in a car. I want to do everything right.