It's probably just a bad electric actuator. Can you manually lock and unlock the passenger door using the **** at the top of the door panel?
The panel itself isn't hard to remove but you're pulling the panel free from the clips. The electric actuator is in the door, screwed to the bulkhead of the outside edge of the door. (3) screws I think, Torx.
There are (4) linkages that attach to the actuator using clever color coded plastic swing clips. You can undo and redo them using thumb and finger.
Replacement actuators can be found on Ebay for around $35 - $65 depending on age and wear. I just replaced mine a few months ago.