I have replaced dozens of hinge pins on all different types of vehicles and that is most likely the problem with this truck.
With that many miles the drivers door has been opened thousands of times more than any of the others, so naturally they are the ones to show the most wear.
First to be sure that it is the hinge have a helper lift the door by the outside edge while you look at both hinges. Pay special attention to the hinge pins as your helper is moving the door up and down.
If it is the hinge pins you will see the movement right there. If it is the welds,(the newer ones are welded in worst mistake GM ever did) so look at the hinge itself and what is moving. If it is the hinge you need to have it welded. That I would recommend sending to a body shop unless you have a MIG welder and some experience. It can be done by someone with a jack and welder but unless you know what you are doing you could make it worse.
To replace the pins it is fairly simple but does require a helper or floor jack, I have done them that way.
Tool required to replace the pins.
Floor jack, they do make a special door jack, (costly and most people don’t have access to them.)
Hammer, 3 or four lb
Spring compressor, handiest tool you will ever spend $10 on, but most parts stores have a loan a toll program for these.
Punch the longer the better, but this can be done with a short one, just be careful not to beat the door instead of the punch. I have used a peace of 3/8” steel rod, but I am a welder and have thing s like that laying around.
Forgot, first you must remove the spring in the hinge, I believe its in the lower one. Clamp the spring compressor on the spring in the wide open position and tighten it down until it is small enough to remove. Leave the spring in the tool until ready to put it back. This is the first and last thing you should do.
The pins go in opposing directions, one goes up one goes down. You will see that right away. Simply hit the pointed part of the pin until it is loose and can be grabbed, if it is that loose you may even be able to pull the thing out with a pair of pliers in the beginning without the punch and hammer.
Then replace the pin and go one to the next one.