Allot of great info above...it is very easy to wire in one of those amps, especially if you buy one with line level ins (no converter needed, advise this approach). Nearly nothing you can do wrong on speaker wiring, just keep positive to positive etc. If you have one speaker positive to pos, and the other pos to neg, nothing bad happens, but sound is degraded.
One big thing, wire the amp and the ground as close to directly to the battery is possible. If you do the ground elsewhere, MAKE sure it is a very good ground. An poor grounding, and you get a ground loop....a whine that varies with engine speed.
I'd never installed an AMP when I did my first one, only hard lesson I learned was the grounding issue....