I'm presently rebuilding a 1976 Tom Boy tri-haul boat myself. And if your wood is anything like mine was, YES everything has to be replaced. The foam that was in my boat was so water soaked that it weighed more then you would even imagine. I think I removed about two hundred pounds of water soaked form from underneath the rotted floor. The transom was rotted and removed, the floor the stringers the raised deck, everything rotted and removed. But if you have the wants, it all can be reworked to give you a very nice boat when refinished correctly. You can read my efforts thus far if you want. It is a 1976 Tom Boy boat, motor, trailer and even the trolling motor project. And I think it is the only one listed on these forums...