I don’t have any experience on these cruisers. But like most boats of this era, they weren’t built well and much of the structural elements were not properly encapsulated leaving the wood cores to become water logged and eventually rot. Freeze thaw cycles exacerbate the process. For areas that you can’t get into, a bore scope attached to your phone can be a great tool. My boat looked great from the deck, the carpet wasn’t even stained. One small soft spot caused me to pull up some of the carpet. What I found was rotten plywood, and I learned very quickly from this forum that boats rot from the bottom up. The carpet was covering up a lot of ugly. That led to a complete gut and restoration.
Open up as many panels and hatches as you can as low in the hull as possible. Drilling small test holes in the encapsulated wood will help you determine what’s wet. If the wood chips are dry, just fill the hole with 5200 and move on. There is a lot of help on this forum as you start looking around. Hopefully you can just replace the portion of the deck you pulled up and go boating. That’s best case scenario.