This is the component that locks or unlocks the car door at the push of a button. There's no need to go to an expensive casa if ever you need to have this part replaced. This kind of repair is super easy. The hardest part is if you need to fabricate a bracket for it.
Do remember that usually an actuator won't completely fail without warning. It will make funny sounds at first. Shop around for the best prices, or go with a surplus part. Sometimes the latter will last longer than a made-in-China replacement.
Do note that water damage will cause these to fail. Make sure your car's windows channels and weather strips are intact.
HOW TO REPLACE A DOOR-LOCK ACTUATOR
1. The power door lock mechanism will fail. The first signs are when it makes a funny noise, and when the actual lock only opens or closes halfway. This is a hassle when leaving your car parked, because you need to physically check all of the doors to make sure they are locked. This is an inconvenience more than anything.
2. First, remove the door sidings carefully. Identify where all of the mounting screws are. Some of them might even be hidden behind plastic tabs. Don't be in hurry or you might break something. Carefully disconnect the wiring harness from the power window switches as well. Peel back the protective plastic which keeps water out and locate the actuator.
3. Chances are, the actuator has metal rods that connect to the actual door lock. This part might be hidden, so be very thorough. It is usually connected to the inner door panel by a few screws. Each car might have a different assembly.
4. Once it is removed, compare the original part to the replacement one. If it has a different shape or orientation, fabricating a bracket might be required. If you went with a surplus part, it should easily fit. Replacement actuators are just P400 to P600. Not bad, right? Don't forget to return the plastic protector of the inside door panel when putting everything back together again.