There are a number of stringer repair threads on here use the search box at the upper right. Some good places to buy materials are US Composites for fiberglass and epoxy. They are very knowledgeable tell them what you are doing and they will set you up with the right stuff. Rotdoctor.com for a product called CPES coat all the wood with 2-3 coats . You are about to start a massive job you have to split the hull at the rub rail and remove the top . Do a lot of research before you start and measure,measure and then measure again. Remember the new floor has to match the top cap sides too high or too low won't work.