If your power locks aren't working, you have a number of options besides buying an overpriced actuator from the Ford Dealership.
If just one of your doors is not working, then you can just replace the actuator and that should solve your problem. I sell power lock actuators for $6 each + $1 shipping.
If more than one of your doors isn't working, then I would recommend replacing your Factory power locks with a power lock system from Ford-Trucks-Power-Locks.com . The kits start at just $29, and I highly receommend a keyless entry system for only $40 more.