LOL,,,,,yes,,finally out, along with a badly torn up right thumb. The top bolt on the amp is just inaccessable, period.
I had to remove the black computer module, and it's bracket, and take a screw driver though the openings of the cast aluminum mounting bracket in order to pry - pop the amp free of the upper most bolt. Nothing broke, but the female mounting clip for the amp bolt, just pulled through the bracket.
As for the freely dangling five pin connector, I still have no clue. It's not part of the amp.
I have a new amp on order, and would be happy to shoot you some digital pictures if it will help, you, or the next guy who needs to deal with this. I now know why the dealer wants $800 to do this work!
I actually had to build a platform outside the drivers side door to allow me to lay flat for a long period of time (used a bunch of bundled boxes laying flat).
When I install the new amp, I will not connect that upper bolt. The other two will hold it just fine.
It's amazing how GMC can put in a 1 - 1/2" (fine thread?) long bolt(s) to hold a light weight plastic bracket, which holds the computer. 1/2" long would have been more than adequate. Same with the amp, which is held with speed screws that are just way too long for what they are needed to do, and take forever to ratchet out.
Nothing appeared wet or bad on the outside of the amp. All the plugs were in tight. I'm 99% sure the Amp is just "blown".