I stumbled onto a silverado/sierra forum post a few weeks ago that explained a little about relocating the USB port on the dash to the top glove compartment so their USB thumb drives were not exposed. I use my iPhone with my USB port and I didn't like the fact that the only place to put my phone while plugged in was the cupholder and I already kept a lot of stuff there. I also had a GPS that I didn't like the cable just dangling across the front of my radio so I decided to explore and look behind the dash. My 2011 silverado interior was exactly the same as my new one so, even though I've only had the duramax for a month now I already had working knowledge of the interior. The dash on my truck came out very easily.
First start on the driver's side under the steering wheel by removing the 2 philips head screws along the bottom of the lower trim piece, and the 10mm recessed bolt that is also along the bottom of the trim.
Then remove the driver's side fuse panel door which is located on the side of the dash by gently pulling the bottom tab.
Then you can start at the far left of the first trim panel gently pulling the clips loose working from left to right. if you have the integrated trailer brake controller be very careful around it so you do not damage the wiring harness. Once the panel is completely loose, unplug the harness from the integrated trailer brake controller to remove it.
Once that panel is removed move to the center lower trim. The first panel that was removed exposes 2 7mm bolts that need to be removed. Only the 2 closest to the ashtray.
Then the ashtray needs to be removed. Be very gentle and careful this is all plastic that is easy to break. To remove pull it down until it stops. then pull from side to side with a little downward pressure until the 2 side retaining clips are pushed out. The back retaining clip must then be pulled up in order to release. Once released the ash tray wil pivot down and pull off of the hinge.
Removing the ashtray exposes 2 philips head screws that need to be removed.
Once the 2 screws are removed the center lower trim panel should easily unclip.
Then starting with the upper right corner of the upper center trim panel working clock wise around it, gently pry the clips free. Once all the clips are free, the wiring harness connectors connected to the lighter socket(s) and usb plug, 4wd, and accessory buttons all need to be disconnected to remove the panel. The left ac vent is recessed very deep and may require you to put the parking brake on and with the key in the ACC position shift to 1, to tilt the panel back far enough to free it from the dash.
That was all I needed to get what I wanted done. The top glove compartment is easily removed by removing the 2 Torx T-15 screws under the lid and pulling straight out to remove the clips. This is just reference, I am no authority. Do this at your own risk.