Far as west systems resin, it is a great product but man it is expensive. If you want to do epoxy resin then us composites makes a great resin for way less money that will be just as good I am guessing. Far as saving money, I use Vinyl ester resin and it will be almost as good as epoxy but for about half the price. I generally use epoxy when I am doing secondary bonds -bonding two fully cured pieces together, (ie: bonding a transom core to old original glass or bonding the deck to the top of the stringers) but for most other standard lay ups I use the VE.
Quaintly wise, I try to buy a 55 gal drum, you can get one for less money than 2) 10 gallon kits sometimes but that is not feasible for most due to the shelf life of 6 months. It will last over a year mostly but the manufacture list 6 months on most resins and by time you get them they are this old usually. I have a drum mixer and mix mine every week and before each use. That prolongs the life by a lot. I would suggest buy most of your other material's like the csm (chop strand matt), 1708 cloth and usables like sand paper, mixing cups, rollers, and glassing tools ect. if you want to stock up on material's. Just start out with a 5 gallon kit or a 10 gallon kit then buy more when you get low so it dose not get old and go bad on you.
Sounds like you have a good game plan, Just remember to keep as much weight forward as possible with the bracket. Balance is very important.
Far as the cloth goes, I would get a roll of the csm, it will cost around a $100 for a whole roll. The 1708 will cost around $750 a roll so you may want to get 10-30 yards at the time on that due to you will not need a whole roll. Get you a good roller or three too.
The core for the transom will cost you around $75 a board for marine grade douglas fir ply wood, If you go composite it will cost you twice that or more.
Buy some thickened agents for the resin like cabosil, micro balloons, talc, and microspheres. They wont go bad.
This explains what each are:
http://www.eagerplastics.com/fillers.htm
Im forgetting some things but others will chime in too maybe.
Just plan on it costing twice as much and taking twice the time as expected then you may get a close figure. But when done you will have a nice classic that you done your self and that is price less!