Can use a saw and go all the way around the edge of the boat. lift floor out in one piece.
It will have a bunch of 5x5 squares of ply, clean all wood off skin, use full sheet plywood 3/4 to make your new floor, after you are done you glass the skin to the ply and sides of the boat you good to go.
as far as the rest goes ask skools hammer and a host of others the best way.
skools did a floor just a while ago, ck out this thread.
http://www.wellcraftv20.com/cgi-bin/...386145;start=0