I'm moving this thread to sticky status, for both fiberglass pools and steps. I'm going to add some notes about FG steps, following this post.

Tap Plastics (http://tapplastics.com/) has some helpful videos:
FG repair
Gelcoat repair 1
Gelcoat repair 2
In many cases, if you want to tackle FG repair, you can find what you need at Lowes, Home Depot, or a local boat supply outlet.

Amazon also sells products that will work in many cases:
Gel-coat repair kit
Fiberglass repair kit