I need help routing the back up camera wire to head unit.

Here is how I did the wire for my 2006 XLE with Pioneer AVIC-140HD: the backup camera wire from the the back of the unit to the glove box, then go through the pillar to the top ceiling all the way to the back. The reverse wire can be connected to the backup bulb wire.

so once you have the wire up in the ceiling, how do you guide it to the back?

along the trim in the ceiling. the wire is hidden behind the plastic edge.

how did you run the wire from the camera out side to the inside?