If you take the back wheel off and remove the nut that makes contact with the hub on the left side (the side that the brake cable connects to) the whole side comes off and the brake pads and all the moving mechanisms are attached to that and slide out of the wheel in one piece.
The kill switch wire:
Touch different loose wires to the handlebars to ground it until you find the one that kills the engine, then just attach a switch from Radio Shack or something that grounds it to the handlebars.
It's probably in the grip.
Take the twist grip apart by loosening the screw on the bottom of the staionary piece and sliding it off of the handlebars and then where the cable wraps around the grip insert, take it off and wrap it the other way and reattach the cable. The twist grip is kind of tricky to reattach to the stationary piece. they will attach when the two pieces are not connected to the handlebars, so monkey with it a bit and when it appears to be correct, slide it back on the handlebars and tighten it up.
Hope this isn't too complicated!