The speakers in the transom is dumb, dumb, dumb.... but since this is an all composite boat, the "harm" in it isn't all that bad. You could pay a pro fiberglass guy $500 to un-do the guys mistakes. I'd talk him down that much to start with.
The vinyl is garbage. Plan for either headaches or $2k to fix that. A good vinyl guy could probably work with the material that is there.
The guy will try to tell you how awesome his "custom" stereo is. I wouldn't listen to him.
Do a compression check and look at how to un-do this guys bad ideas. It's a solid boat with a lot of potential. Get him down a bit on the price and you've got some extra money to start with.
Former owner of a 1987 Supra Saltare. Current owner of a Malibu 23LSV.