taks.
yes, easiest way to do earth, is to put it under a bolt that is connected to an unpainted part of the chassis.
as to the 'do i have to solder' thing. u can crimp them, but u still have to cut the wire, strip it and then crimp it up.
easiest way ive found...if u have the room is to get inline crimps. soooo much easier
all u do is slip it over the wires, and push down. and a piece of steel slices into the wires, creating a connection