There are gonna be a number of ways to do the transom just with the chainsaw and pour method keeping the inner and outer skin intact. Any of these may involve just cloth and resin or combined with wood, fiberglass panels or even composites. Or pouring with something from West Systems, Nida-Core, Aray or the like.
To me, this would be an excellent opportunity for you to do this work just for the pain and experiance of it. Up to $4k for someone else to do the work wouldn't be beyond possibilities. This should prove to be very labor intensive, materials alone could run $300-$600.
Search the threads, internet, get opinions of transom repairs. Mine is do it yourself, if possible keep the inner and outer skins intact, decide on a pourable material to use either with or without composites or fiberglass panels as fillers, wood rotted, don't go back with wood.
Several guys here have done transom replacements, they will chime in.
This is mine from getting it to the house & to the water, almost 5 months time lapse.
http://www.wellcraftv20.com/communit...ighlight=specs
(and work still continues)