Can you tell us what year your Astro is?
Here are the instructions, which is pretty much what the guys at the yard said.
REMOVAL & INSTALLATION
See Figures 1 and 2
Fig. 1: Rear door hinges
Fig. 2: Rear door check assembly
Disconnect the negative battery cable.
Remove the door trim panel on the right door only.
Disconnect the wiring harness from the license plate lamp and power door lock, if so equipped. Remove the harness from the door.
Disconnect the check strap from the door frame.
Drive out the hinge pins while an assistant holds the door in place.
Remove the door from the vehicle.
With an assistant, install the door onto the vehicle.
Drive the hinge pins through both hinge halves.
Connect the wiring harness, install the trim panel and connect the negative battery cable.
About all I could recommend is that you try to get some penetrating spray in there to loosen up the pin, or perhaps apply a little heat to make the outside expand a little. These can be a real pain once they have been on there for some time (like 20 years or more).
I hope this helps.
Take Care & Good Luck, Greg A.
Thank You for the Accept & Feedback.
Take Care & Happy New Year, Greg A.