I have fixed several of them. Previously I just used the polyester laminating resin and it did not hold up well. I have since used the epoxy and time will tell.
Yes you must dry out the wooden core. It really looks like masonite and when wet turns to mush. You will likely need to remove the underneath layer of gelcoat and resin and remove/scrape out the mush and reinstall some type of structural material. I used a dremmel to cut a square out from the underside then srape out the crap. I used a masonite material again and made sure to seal it well particularly around the hinge screws. It seems that there was insufficient gelcoat around the bottom edges and moisture wicks up into the core and causes delamination. (much more sever in northern climes with freezing temps). Same issues around the hardtop edges. I am hoping the epoxy is less prone to moisture absorbtion. I also built up an inner radius using layers of cloth and resin to increase the strength for the panel. My edges are now about 1/4 inch thick. On the starboard fish box lid I added another 1/2" of plywood as well to increase strength. I think that flexing when sitting or stepping can cause radius cracks which allows moisture to be drawn up into the core. A dremmel or small angle grinder/sander would be a big help here. (Harbor freight about $15)
As far as the gelcoat color, I was not successful with the Spectrum color match and have since been mixing my own tint. I start with white base and add a tiny bit of red, yellow and black tints. Check out the Jamestown Distributors website for some good how to videos. Structural repair and gelcoating.
http://www.jamestowndistributors.com/us ... Additives+
Get some prices from some boat repair facilities to rebuild them. Mine quoted like $200 each which was still too much. I didn't spend that to repair 2 hatches. Another option would be to repair the structural yourself and have them shoot it with gelcoat.
Good luck and ask questions.