Currently my 08 King Ranch has the 6CD changer with XM/Sirius and OEM sub. I'd like to change it out to the OEM GPS unit. I've found a few on Craigslist for ~200 out of Expeditions they are parting out. From what I've gathered the 2008 has the amp built in. Are there any parts outside of the unit itself I need to be sure to pull out of the donor car? Is there a separate GPS unit? Also has anyone had experience adding a backup camera to one of the OEM units?