Ive put it in the 04 I had just like it would have come from factory, Needed the front and back speakers, the monsoon amp, the 6 disc headunit, center dash speaker, and the full body harness, and dash harness.
To change the harness you pretty much have to strip everything out of the interior down to the metal.
As others had said you can simply use an after market amp and stuff and it would not be nearly as much work involved as what i did.
I added the monsoon along with many other things so changing the entire vehicles harness was the easiest, then i had the wiring for heads up, xm radio and everything else.