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You will find that overtime the mechanism has, most likely, gotten seized up with corrosion. I attached procedure for removing the panel. The diagram shows the hidden screws and the rest of the panel is held on with posh pins. Slide your fingers under the panel and GENTLY pull. You will hear the door trim pop off and keep moving your hands along the door to the next pin.
Once the trim and moisture cover is off, roll the window up and you will see the latch and door lock. Spray some penetrating fluid into the lock and around the latch. Let it sit and them gently attempt to operate the outer lock with the key and interior lock from inside at the latch by moving the rod.
I find removing the latch as an assembly and lock and doing it on the bench is easier; however, depending on your expertise and tool availability, you may want to keep everything in the car.