New here & looking at a '91 Cajun Brute 3

I have a line on a cheap 1991 Cajun Brute 3. Titles for everything, but I need to know what I should be looking for in the way of damage. Boat was in a barn until about 2 years ago, after that it was parked outside, but where it could drain. I thumped on the transom to see if it sounded solid or if it sounded dead. Sounded ok, but I may not know what I'm listening for. I can't take the motor off yet to inspect the holes to see if it's wood or composite transom. How can I tell if it's a composite?
I also poked at the floor. Even though it drains, the trees that it has been under have dumped enough debris & crap in the floor, that it holds moisture on the deck floor, so the back corner near the passengers seat seems a little soft, but not too bad. My question here is do I have to take the top cap off the boat to replace the floor if I need to do that? Or can I cut it, use it as a template & slide new decking under the cap? I'd rather not de-cap it if I don't have too.

It also comes with a second old fishing boat with titles for everything.