repairs
Before I went into replacing the core I would certainly first try one of the chemicals that are supposed to dry, and fill in the wood core where it has gotten wet. try west marine or boat us, i know I've seen this product in their catalogues.. for the non skid the normal method is to 1. put a light coat of wax and a releasing agent on a piece of adjacent non skid, 2.use a liqud type of molding putty to make a mold of the non skid surface, then 3. use that mold to prepare the surface of your non skid when you put down your gelcoat in that area. the mold will help the gelcoat cure and insure it cures in a pattern similar to what exists on your boat.. there will be mis-matches on the edges where the old meets the new, but probably only you will see them.Good luck,Nate