I am also not a pro glass guy, but I can give you an idea of where to start.
First you're going to want to use a wire brush to clean out debris in the area of the damage.
Then you're going to have to grind back gelcoat around the damaged area (at least an inch all the way around).
Then you're going to need to get some bidirectional glass cloth and cut out 3-4 pieces that will cover the damaged spot (out to and including the area where you ground off the gelcoat.
You'll also need epoxy with the "slow" hardener.
Saturate the damaged area with epoxy (not so that it's dripping, but totally "wet." Be sure to get it in all the little crevaces. A small paintbrush is good for this.
Then mix up some epoxy with "chopped fiberglass" or "flox" or the thickener of your choice until it's got a peanut-butter consistancy and use it to fill in any gaps or holes. Work slowly, you might have to do this in more than one "sitting." You're doing some basic fairing here to give the glass a form to follow, so try to make the flox mixture roughly like the shape of the hull, except don't come all the way out to the full "thickness" of the hull because you'll be adding layers of glass and more epoxy on top of that and you don't want it "bulging out" either.
Then "wet out" the damaged area again with epoxy and place your first piece of glass over the area and make sure it sticks all the way around. Use a small paintbrush again to work out any bubbles you see under the glass. Also use the paintbrush to make sure the glass is saturated with epoxy. Then apply the second layer of glass, etc. You'll have to keep dabbing more epoxy on as you add layers of glass to keep them saturated. The fiberglass layup is the most fatiguing part of the process, I think.
When you have all the layers of glass on then leave it alone for a few hours or overnight. Around the edges where the glass meets up with the gelcoat you can sand any rough edges and/or trim excess glass with a Dremel and a heavy duty cutting wheel.
THEN mix up more epoxy with Microbaloons until it has a frosting-like consistancy and slather it all over your repair and into any little crevices around the edges of the repair. Build it up higher than you really want, and make sure to totally fill the weave of teh fiberglass, because when this epoxy cures then you'll sand it smooth and fair. Now it should be totally repaired except for the aesthetics. You can paint it or do whatever. If you get some gelcoat dye from West Marine I've had good luck mixing that with epoxy, so after testing it to make sure you don't have any problems with the epoxy curing after adding dye, you could add the dye to the microbaloon/epoxy mix to color-match the gelcoat. That's just an idea.
Anyway, good luck!
