I just bought a kit from Academy (or West Marine, I don't remember which), had decent instructions. Turned out OK for a first time job. The chips ended up looking better than the cracks. I would most likely make my cracks into chips if I did it again.
EDIT--I think it was purchased from Bass Pro Shops. Either way, it has a small amount of gelcoat material, and various color tints you can add. I just used a bunch of white (gel coat was a clear-yellow color at first)
Go get a gel coat repair kit from West Marine. Read directions. It's really easy. Just take your time. I've repaired my skis a few times and you really cannot tell where the damages were.