The fold out panel should be pretty easy to remove. Likely just some torx screws.
Yeah my guess is that I had room due to the Crew Cab extended back seat area. Under the driver seat, or if you have the guys to pull your rear seats, you could mount is on the rear wall, but I hate mounting amps on their sides.
I this photo you can see the 12v source I used. It was a light blue/orange (I think orange) wire that had switched power only. It was a wire that went to something other than audio peripherals (i don't know what it is used for honestly). Also in the picture on the upper left, you can see the black box with a couple wire harnesses (one white barely visible and one black). That box is the built in amp for the stereo system. The black harness with the green wire in the picture is the 22 pin harness listed in the post with the wire diagram.
I'd say you could tap the LOC into the white wire harness:
pin 7 gray with dark green stripe (LH rear door +)
pin 8 gray with light green stripe (LH rear door -)
pin 9 green with yellow stripe (RH rear door -)
pin 10 green with gray stripe (RH rear door +)
if the colors on the 2013 match of course.