I'm no expert and have never done it myself but I can offer the follwing advise whihc may or may not be a load of crap (i'm sure the clever folk of this forum will correct me if I get it wrong).
Have a look at www.cfsnet.co.uk
for all GRP supplies. They're cheap (their prices on the web are however EX VAT) and there resins come with catalysts.
I don't really know how many layers you should apply but it sounds as if the plywood shell would be enough on its own to stand up to all the forces involved? If this is the case then I would say only 1 or 2 layers of 300 or 450gsm CSM. Or maybe 2 on the outside and 1 inside. This way the wood will be encapsulated and impervious to water etc.
After this has been done I think you will then need to apply a layer of tissue which helps to cover up the rough CSM pattern. You can then flowcoat it (Gelcoat with a wax additive that means it will dry in air) to produce a very hard and resistant coating. This coating will however not be glossy so then you need to shine it up with wet and dry and a cutting compound. Alternatively I think you could use a 2 pack polyurethane paint that will dry hard and durable but will be glossy.
what ever you do good luck! I hope others on this forum can either confirm what I have said or correct me where I have got it all wrong!