[captj2]

I replaced my transom from the outside leaving the inside f/g face in place. The wood was wet for the most part and a hammer and chisel worked pretty well but I also used a side grinder to make a square pattern of deep grooves in the wood. This made the chisel more effective and broke the work up into manageable sections. The grinder, carefully used,can clean most of the wood from the remaining f/g face and the transom edges,leaving a good surface to adhere the new wood.I used 2 sheets of 3/4" marine plywood. Whatever plywood schedule you use,dry fit each layer first to check your clamp setup.
Good luck.