Wiring aftermarket DVD System in QX56

I have completed the installation of a Myron & Davis DVD headrest system in my 2006 Inifiniti QX56.  All but the actual connecting of the wires to ground (black(, power (Red) and memory power (yellow).  I haven't installed anything in a car since mid-80s when there were simple fuse boxes under the dash.

My questions are:

1.  How do I select wires under the dash to tap into in order to power the new unit?  There are a couple empty wiring harnesses under the dash, do I tap in to those?  OR  ...Do I vampire tap into some existing wiring to power the units.  IN the dark here and don't want to pay $300 for 10 minutes work.

2.  What are the wiring colors in my Infiniti?  Same as this unit? ground (black(, power (Red) and memory power (yellow). 

2.  Do I disconnect the battery before wiring anything?

thanks in advance.

You should be able to get your wires from you igntion harness. You can also use wires for the power windows that runs through the car under the plastic panels of the floor. Its up to you. But You dont have to disconnect your battery.