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These aren't hard to replace and are of the same style common to most GM products of the era.
You can either remove the door completely or replace the pins and bushings with the door in place. If you have a helper it will be easier to disconnect the door wiring harness and remove the whole door, if you don't have help to remove the door then it may be easier to protect the surrounding paint with masking or duct tape, remove the pin from one hinge at a time and use something like a floor jack to help support the door while working.
There is a pin in each hinge that will need to be driven out. One hinge's pin will be driven upward, one downward to remove. You first need to remove the springs using this tool. The arms go into the springs and the bolt is tightened to compress the spring and remove it.
Then the pins can be driven out and either the door removed or work on one hinge at a time. Remember the wiring harness will need to be disconnected before removing the door if you do it that way.
After the pins are out then the bushings will be driven out of the hinges using a punch and hammer, the new bushings tapped back in, and the new pins driven in.