Foam is a tricky thing. When I did my Islander there were areas that were water logged and other areas that were bone dry. I suggest that after you take off the floor boards you check if it is necessary to do the foam. As for the cabin. I just took the separating wall apart and removed the side seats. When you pour the new foam,you should lay a layer of bubble wrap in the bottom. That way the foam does not stick to the bottom and there will be drainage under the foam. Also glue a plastic sheet to the floor boards,so the foam will be protected from water on the top. If you do not do this,the foam may be water logged again in just a few years.