2007 RL - 108k miles

The driver's door lock use to lock/unlock about 50% of the time with the power lock but now it will not lock or unlock when I press the keyfob button or the lock/unlock button on the door. I have to manually move the lock from the inside to lock the door or use the key.

I have looked and cannot find a DIY to replace the actuator. Has anyone done this and how difficult was it, how expensive of a part is it to be replaced? Or is this a job I should have the dealer repair for the car? Any help would greatly be appreciated.

 

I can't recall a DIY here, but it is a reasonably common failure on any car. It may be worth searching the 3G TL forum for any insight as I know they have seen it too.