Using modern crankest on old Schwinn?
 

I have a Schwinn Voyageur, which has served me well, but for real utility duty I'd like some lower gearing. The bike is (IIRC) a 1981, with a six speed uniglide cassette rear.

Performance is clearing out campagnolo cranks, and I realized that a Centaur compact would be cheaper than a regular cheapo nashbar compact crankset, and was trying to figure out whether it would work with the drivetrain that I have. I assume I would need a different bottom bracket, but other than that, are there any issues to worry about?

I don't know why it would require a new FD, but I am open to any thoughts/criticism/advice available.

If you install a Centaur-compatible bottom bracket, you should be good to go, unless your chain has elongated with use. If you are keeping the 6-speed cogset, you will want to stay with an "8-speed" chain.