For your 2007, it's actually even easier.
If you buy the GM kit, it includes everything, including a harness which plugs in under your dash to power the kits. Basically, it entails:
1.) Remove old headrests...an icepick in the small hole on the inside of the post mount and they pop right out.
2.) Remove the plastic seatback. This is the toughest part of the whole job. Start at the bottom and use a trim removal tool. If you break the tabs which hold it in place, it won't go back on properly and you will have to replace the panel ($80 apiece - I know from experience.)
3.) The headrests drop into the holes and the wires get fished down through the seatback. Plenty of room to do this.
4.) The wires come out at the bottom of the seatback, there is a hole in the frame.
5.) Remove your center console, cupholder assembly by pulling up on the back of it and sliding it backward after the clips release.
6.) Run the wiring under the seat track so it doesn't get pinched, then up into the area under the cubby. The side panels of the center console have enough "play" to get the wiring through there.
7.) Run the power harness from the area under the cubby toward the firewall, then either up above your feet or down low under the carpet. You want to end up at the junction box to the left of the brake pedal mounted on the firewall.
8.) Pop the cover off...there are two open plugs on the left side....plug the harness into the 2nd one from the bottom.
9.) Connect all the wiring to the junction box. Everything is color coded so you can't hook it up wrong.
10.) Tidy up the wiring...mount the junction box underneath the cubby with 2-sided tape. Reinstall the cubby (snaps back in.) Reinstall the seat backs (carefully...line up the tabs so you don't break them.)
11.) Enjoy
