Do you have a GMC maintenance manual?
If the door is still on the truck, I'd leave it there until all parts are removed. Remove the cardboard panel from the door and remove the metal cover on the lower hinge side of the door.
If you are intending to remove everything, start with the window and then the window mechanism. Then, the door latch control rod/assembly (or, I think you could remove this first).
One bolt at time - label and bag all bolts/nuts/washers.
The GMC Maintenance Manual has instructions for removing the window, window regulator, and the door lock assembly.
