IIRC, you have to remove the map pocket/garbage can pod that runs the length of the door.
Those were put on at the factory with the plan that they'd never be removed.
There are platic pins molded into the pod thingy, pushed through holes in the main body of the the D/P, then melted over on the backside to hold.
Can be removed with a small hand-held butane torch & a pair of needle nose pliers.
Heat that melted over part of the pin & working quick, pinch & reshape it so that it can be pulled through. Try not to remove any of the pin's material. Work one at a time.
Re-install...heat a flat blade screwdriver & remelt the pin.
I've heard of some re-installing with screws from the backside. Have to grind some length of the pin that pokes through the D/P for that, then use what would be left of that to screw into. But seems to me that there's not enough diameter of what would be left of the pin to get a screw large enough on there to actually hold that pod.
I have seen other's where the pin has a collar molded & then held with flat one-way push-on clips. Much easier to re-&-re. The little collar has to be sacrificed to remove. But then the melting over proedure could be used when installing.
You may find that that pod is also glued in spots. A putty knife, a heat gun & patience will get it. GM used some tenacious bonding agents.