One other thought, if you want to try the Dremmel tool route, and it is not too great an area, then you can use a flexable shaft. You can work the bit and shaft in several inches and still have good control. I prefer the Roto Zip with flex shaft--same company. There is more torque and it seems more substantial than the Dremel tool flex shaft.
Cutting out the top deck is not as hard as you might think, and texturing gel coat with silica will make new non skid to blend in where the cuts were made. A Fein saw would be best for cutting, but there are several (like Makita) very narrow blade circular saws (also Rotozip makes a very fine saw blade which will work on the deck for cutting off the top layer, if that is necessary.