Assuming you need a new crankset (three chain rings and two pedal arms), this is not as big a project as you might think it is. As I mentioned earlier, I replaced the crankset on my 1996 GT Outpost a few months ago and the part was readily available at a local bike shop. The whole thing, with installation, cost me $40.

If you have trouble finding one, call Dan at Visentin Bike Pro Shop in Oyster Bay, NY at 516-922-2150 and he can probably ship you one.