lift gate will not open

First, check for any blown fuses -- a blown fuse will prevent electrical power from reaching the latch actuator. Second, if if you have the interior panel removed, you'll need to test the actuator in the rear hatch. Check for power and ground. If it has both and the actuator won't work, it will need replaced. If you have the rear panel off, you should be able to manually release the latch via the inside cabling to open the hatch.

The same thing just happened to my 2011 Yukon. My dash is also a mess. Did you happen to fix your lift gate?