So today my driver side door decided to stop locking with keyless entry, lock button on the door panel or the button on the remote. I hear something try to move, but it doesn't move it down or sometimes partly down. The passenger door works fine with all above stated options. Manually opening the door from the inside works fine as does using the key from the outside.

Is there a motor in there somewhere that needs to be replaced? I hope it's not expensive.

 

It's not a motor but a solenoid. It's not necessarily hard to replace but it is a challenge. When I did this on a 97 F150 the solenoid was held by rivets so you may need a rivet gun. The rest is just an exercise in contortion. Recommend you get a manual from the auto parts store and read through the instructions.