Mike,
Repairing 'glas is pretty straight forward. I've done numerous repairs on boats over the years, from patching small dings to a few larger repairs.
But to get a nice finish in the repair of the size you are describing it will be about a 6'' plus area to feather every thing in.
West System(Available at most marine suppliers like West Marine here in Seattle area)is one of the best.
http://www.westsystem.com/.
I've used it and it works, follow the instructions to the letter and you end up with a great repair ready for paint. Much better than the typical fiberglas repair kits you find in hardware and auto parts stores.
I repaired a ding that broke through the 'glas on the cabin top on our sailboat after I dropped a wrench from the top of the mast about the size you have. The resulting repair was an area about 6'' in diameter. Tinted gelcoat to match the rest of the boat after about 6 mos you could not see it unless you were really looking, but that is gelcaot over paint.
Hope this helps