I replaced the transom in my 2003 Lund 1600 Prosport this past winter. I used marine grade plywood (2 layers of 3/4" laminated with waterproof adhesive and screwed together)coated it with epoxy after I predrilled my bolt holes. Prior to bolt installation I put 3M 4200 in the holes to ensure a complete seal. I replaced any foam that I took out as my marine mechanic told me that this ensures proper ballast. I sealed the top cap prior to installation(Lund doesn't do this which was a big factor in the rot to start with.)with 4200. Total cost which included removal/replacement by my marine mechanic and parts was around $1200.00. Not a tough job, just takes a bunch of time.