Take a look for a book (or Google) Fiberglass repair or boat repair.
There are lots of good resources.

If you live in an area that has a TAP Plastics store, they are a good resource for supplies.

The 'kits' are just small prepackaged fiberglass patch kits - pretty generic.

I think the one thing is that you want to use an epoxy-based resin for strength.
If I recall correctly, you want to cut out the crack rather than try to patch over it.

What I have done is:

Cut out the crack with an angle grinder or dremel.
Patch one side with mat. (top)
Fill the gap with cut fibers or "chop"
Place a second mat over the chop on the other side. (back)

Sand and prep for painting.

Its pretty fun, actually - make sure to wear gloves and a mask to avoid breathing fiberglass shards.