Hello. I would rip off all the old ply and upstands for hatches etc and plain/gring off all the old membrain/soft bits you find and allow to dry. Remove rubbing strates. For the ply I would use WBP, which use's the same glue as marine ply but WBP in not Lloyds approved. That will save you about 3/4 the price. Although, I would use 9mm ply as this would be strong in its own right with the aid of the camber. When deck is ready trim into coachroof etc and leave plenty of over hang so someone can pull down whilst you screw into beam shealf. To stick the ply down I would use Polyuraphain glue. The gold colour stuff that foams up. This will go into all the t&g and any other bits that have been ground out and is salt water proof, flexable and strong. When gone off trim up, put upstands back on and round over edges and put epoxy fillets on any joints then epoxy shieve onto coach roof (rebate could be added for this or prep and glass the lot) and 1" 0r so down hull. This is the fastest and easiest way of putting on a new deak that will last indefinatly if all deak fittings are bonded down correctly. Hope this helps, but rember if you ask 10 diffrent people, you get 10 diffrent answers.