I just realized that you already mentioned that he may be burning fat, etc. and then I did it again. Sorry.
Eddie, take your vitamins of a full stomach - after breakfast is good. If it is a two or three tablet dose, then separate them. Don't take a multivitamin right before a workout.
Vitamin Shoppe has better selection and pricing, if you have one near you. Until you find a way to order online.
N-Large is basically whey protein concentrate, maltodextrin, and fructose. The fat comes from lechitin. This pretty much follows the line of most gainers. They're convenient if you can afford them, but you can easily make your own and save a bunch.