what kind of cranks did you have? What is the new crank set you're getting? Do you know the chainline of your current rear set-up? Was the chainline pretty good before?

Changing cranks isn't a big deal at all, in m experience. Square-taper BBs can be a pain, though, depending on the condition of the threads in the shell. You can always get it tapped, if need be, although you might want to find a new lbs if you have no confidence in the current one...

-rob