Canuck When I was 13 I took apart my first motorcycle DIdn't know any better and that's how I learned. When I think of it, the $900 that bike cost was as much to a 13 year old as 35K is to me at 52 so what the hell. The only way your really gonna learn is like most of us, by effin it up and havin to fix your mistakes. You'll be ok, just remember the story about the Heart Surgeon and the mechanic.
Quick and easy answer to your question is A) yes it's under the seat B) the terminals are metic not American Standard because the battery is from a Japanese supplier 10mm for the nuts on the terminals. C) most likely the directions for the heated vest will reference the manual somewhere so you need that whether you feel like dealing with 400 pages or not. You only have to read the section relating to what your doing at any one time Remeber Gahndi "A walk of a thousand miles begins with one step " You'll be fine dude and we're here for you when you need us