First, it is really easy to do but the sound will not be AS good as if you had aftermarket.
Here is how to run the amp:
You need to run a power wire from you battery to the trunk, so either get an amp wiring kit with 8awg wiring or bigger (I suggest 4awg personally). You will also need a high/low level convertor, you can find it at Walmart, or any audio store dealing in car stereos (here is a link to what I am talking about
Convertor.
Run the wire through the rubber grommet located behind the battery on the firewall and under the carpet - remove the driver kick panel as well as the door jam panels which hold the carpet down along with the bottom portion of the B pillar and bottom part of your rear seat. Then pull the wire through and tuck it down, pull it into the trunk, and you are done with that. You also need to clear some spot in the trunk of paint, and perferably use a screw already in the trunk, or bolt, and attach your negative cable to it. MAKE SURE there is no paint left.
Now, you have to remove your center HVAC controls to access the stereo. On the back of it you are going to have to locate the corrcet wires for the rear left and right speakers. You are going to have strip back the wire and reveal the copper. Than you have to connect the wires from the input side of the convertor to it, following their directions. Then you can run your RCA plugs to the amp, down the middle, not the same side as the +wire for the amp.
Now you have to locate a remote source which turns on with the stereo, usually the +accesory wire switched ignition. Tap into the same way as you did with the speaker wires, or just cut it in half (like I do) and connect it all back together.

Run this wire down the same side as the +amp wire.
Then just make all your connections like you are supposed to the amp, etc, and you will be rocking!
Sorry, if I had more time I would look up wire colors, etc for you, but it is late and my wife is telling me to get off of the computer!
