Good luck with your project, your approach has potential for excellent success (removing the cap) Replacing the stringers is a huge job which I have zero experience.
In regards to the Transom you have two options pour or plywood its up to you since you have the cap off the sky is the limit.
Shop around for resin and materials I personally recommend Fiberglass Services, excellent price and delivery options ..
http://www.fiberglassservices.com/index.htm
They have a new location closer to you see below ??
3851 62nd Avenue North
Pinellas Park, FL 33781-6007
(727) 525-0830
Your marine grade ply from
http://www.dixieply.com/tampa.shtml#about
BTW here is nice video on youtube ..
http://www.youtube.com/watch?v=7gY1ZJwIJAI