i haven't seen STEP BY STEP instructions. but its not hard to figure out. take the wires out from the stock amp, run them to the new head unit wires(may need some extra cable for length) and there ya go. the wire diagram can be found in the FAQ section.
You drop the glovebox, and to the right is the amp. You can test the wires with a tone generator or a 9V battery to determine which wires do what. Run those wires from the amp plugs to the outputs on your head unit or amp. Remember that you need to replace the rear speakers for it to sound right, as the 2 speakers in the back are stacked mid/woofer, and would present a 2 ohm load to the audio source. Or you can do what I did and rewire each speaker individually. You can get wire at any audio shop, 2 rolls of 15 feet should do you well. Good luck in your endeavor.