If I was to build a boat again, I would probably supply the MDF mould (or design) to a professional fibreglass builder and ask them to build the hulls and I would finish them off and fit them out. They've got the tools, experience and time. It's a compromise between saving costs, saving time, and doing the job properly. It will cost more than building yourself, but you can be fairly sure the finished product will be good, and it will cost less than buying off the shelf.

I have a lot of experience with designing and building boats, I'm a practising engineer in naval architecture so I know something about designing boats. If you know nothing about hydrostatics, performing weight estimates, fibreglass structures, etc, you probably shouldn't consider designing and building such a big, highly loaded boat first time. I've previously built a moth with some friends and it was similar to this build, but also completely different because of using different materials and the small increase in vessel size has big implications for the logistics of building. For certain tasks, I don't think I could've done them myself. At some stages we had 4-5 ppl working on the boat at the same time (mixing resin, applying resin and glass, applying peel ply), Yes, I have a lot of ppl to take for a ride when it's finished! Just moving a hull around is a two person task.

The 12 foot skiffs often use this techique, buy a proven hull and deck off a professional builder and finish it off yourself. The sense of achievement will not be far off building completely yourself, and you will be thankful that you did not do the whole thing, especially if you are relatively inexperienced with composite construction.