You are probably ahead of me on the panel removal but if not, the panel itself is not difficult to remove. There are 5 screws total, I think, holding your 78 panel on if its like my 82 and I think it is. Two of the screws are in the bottom of the armrest. The third screw is clearly visible near the top of the panel close to the outside door handle. Forth is on the lower left corner of the panel . The final screw is INSIDE of the map pocket on the door panel. Once the screws are off the panel can be pulled out slightly at the bottom and lifted UP to lift the panel off of the door. You will need to push the panel toward the front of the car slightly to allow the lock knob rod to clear the hole in the door panel. IF you have power door locks, dont lift too much, only enough to get your hand behind the panel to the power door lock switch. The large flat plug that attaches to the door lock switch can be stubborn to get off, just be gentle and work it back and forth to pull it from the prongs of the switch.
It's been a while since I have worked on my door lock and have NO pics of the interior of the door panel so Im not going to be much help on the interior part. Once the door panel is off most of the guts are visible with the window UP and out of the way. The snubbers arent difficult to get to and the connecting rods just need to be traced and determined if they are still attached. There is an access panel that unscrews to allow more access to the lower portion of the door interior.