Do you happen to have a picture of the stern of your boat? Or a link to a picture of one similar/same model?
"Fiberglass repair" and "finish gelcoat" are definitely two different things. It's kinda like a mechanic vs a painter. Some places have both on hand - some do not. I actually like, based on what you wrote anyways, what your first guy is saying. Does sound like a high estimate. But, yes, skinning the transom is a good way to do it - which also alleviates much of the cosmetic work. If you're OK with the "cut area" being not as nice as the rest (but functionally sound), this might be a way to go and talk to him about a more accurate quote. For me, on a 30-year old boat, I'd be more interested in function over aesthetics. Not that I'd want it to look "junky", but it won't be hard to get it back to (aesthetically) 90% of what it is now.
I doubt you'll find a reputable person quoting less than $3K, though.