I agree, you'll find more wet wood then you think. Cut a whole larger then your work area, be sure to cut on an angle 45* works well not too deep, don't want to cut the stringers. Sand/grind area of floor outside whole to take new glass. Epoxy all the wood, place it back, and begin by glassing the patch back. Start a few inches larger then the wood you replaced and then a secon piece larger then the first. You should be able to paint back or maybe even tint the repair to match.

That's how mine started, now she sits in the yard with no floor at all. Or maybe you just need a new access hole and a hatch, then no replacing anything.