You may want to rethink fiberglassing the interior floor - water has a way of migrating into wood, even when sealed like this. It's prudent to allow a way for the structure to dry out - oil finishes allow this - that's why this approach is so popular.
Kevin, there is a search function located at the upper right-hand side of the main page. I just looked up rebuilding a boat and found that there were four pages of posts that corresponded to the query "rebuilding a boat". I know that over the years I have personally provided a response to a similar question as yours. Take a look there. Try asking a question rather than just a word or two.
The basic thing that you need to determine is the condition of the wood. Old paint covers a multitude of sins and rot. A sharp pointed object will tell you a lot when you try to push it into the wood. If you can't easily push it into the wood your good! Old drift boats often have had water sitting in them and the frames suffer. If water gets into the plywood it can travel and provide an excellent atmosphere for rot.
Let us know what you find. Anything can be fixed, you have to decide how much money, time or effort you want to invest!