It's very very hard.
remove rubrail & top cap, dig out all the old wood with the cutting tool of your choice, fabricate a transom from 2 or more pieces of plywood laminated together and reinforced with fiberglass, fit it into the shell, glass it in, drill & seal drains, pump intakes, outboard mounting holes, replace top cap & rubrail. rehang outboard.
but people are doing it, check the restoration forum at
http://forums.iboats.com