Welcome to the site Steve. Nice to see a fellow Pats fan.
I have zero experience with the Seacast product. I have worked on a previous boat by cutting the outer skin off the transom and re-doing it with epoxy laminated plywood. It really wasn't too bad of a project.
I'm sure you've already searched the site for others that have done this project. You should also check out
www.classicseacraft.com ,
www.classicmako.com , and
www.classicaquasport.com
You'l find a lot more info on those sites as well. Take some pics and show us whatcha got.