Give Joel at precision fiberglass a call. He is in West Sayville - 218-2524. I used him last year for some glass work on my Mako. Very nice guy, and job was well done.
I can second the opinion about Joel in West Sayville His glass work is the best I have seen in that area.He fixed a hole in my boat a few years ago after someone put their bow pulpit through the side, matched the paint perfectly and three years later you still could not tell the boat was patched
" be your own " glass guy.
I've done deck work & some small holes & more but a transom , I'm not sure if I would tackle that but maybe ..
Check Iboats.com restoration forum do a search & or post it.
You'll get a good idea there what your in for & how it's done ..