If it's a non-premium sound system there is no amp to bypass is you want I have a set of instructions from Crutchfield for the HU install. And like mentioned go with a newwer cheaper Pioneer, I've heard a lot of good things about them. (I'm a Kenwood Freak Myself).
You can spend an additional $8-$10 dollars to get the wiring harness that way you won't have to cut any of you stock wires. WHich is cool that way if he goes to sell or trade in the car it'll take him less than 10 minutes to put the old head unit back in.
Here are the Crutchfield Master Sheets As you can tell by the sheets it's not that hard at all especially with the wiring harness.
