#2
it's basicall the pickups pots, switch, jack, all the wires and any thing like the fernandes sustainer kit
#3
everything including pickups, tonal and volume knobs, pickup selectors, ground wiring.....basically anything electric on your guitar
#4
I'd say there's not that much in a basic guitar, (electric) It depends how many different controls there are. If there's a tone knob, or two, or if even more probable a volume,or two, nearly all have that one... Exceptions of course, but why not keep it simple? So that would mean the necessary wiring for, let's say the pickups > volume > the jack > amp. Did I miss something?

Hehe, or maybe a Gibson Robot, that's a little bit to much xD