Make Your Own Electric Guitar by Melvin Hiscock (made up name) is my Bible. A course would be great if you were thinking of making a living out of it, but personally I'd get a good book and start building using cheap timber to start with, I made a jig that I use for fingerboard profiling and fret slot cutting, it was done on the cheap but works well. You can start of with plywood for bodies to get used to using a router and jigs for neck sockets, pup cut outs, control cavities etc then move on to decent timbers as you gain confidence. My next build is going to be a 64 P Bass, veneered board, vintage truss rod with body end adjustment, clay dots, etc