Steve,
I'm in the middle of replacing a lot of the interior panels from my H34 due to rot. I just finished replacing the main cabin sole with 3/4 Holly and Teak plywood. I used the old panels (as much as was left) as a template. Cut the plywood and test fitted it. Then took it home and applied an epoxy to both sides, then 6 coats of a AWLGRIP to the top. I then replaced the side cubbies with new wood. I purchased 1/2 marine plywood and then either an off-white or natural teak Formica. Most of the replacement wood is inside the cubbies and what does show matches the remaining real teak. Again, I used the old pieces as templates. In some cases, I screwed the old piece to the new piece and then used a router with a pattern bit to duplicate the original, and then applied an epoxy coating after a test fit.
One of the hardest parts was removing the bronze screws, in some cases I just took a 4 1/2" grinder to cut off the old rotted panel and leave the teak unharmed. I didn't want to try and remove the screws that were countersunk into the teak and capped. I then screwed the teak back onto the new boards from the new board.
You can get new bronze screws by the box or get some stainless steel screws for the refit.
As for the fiberglass, it might be that the fiberglass is holding the wood in place rather than providing structural support. Regardless, You can probably pry it off or cut it and then get apply a new piece of fiberglass once you have the new wood in place. Fiberglassing isn't rocket science. Probably a youtube video.
