Door Clicking When Locked 2004 Sport

[Maka]

Just bought a used 2004 Sport- I think I'll love it.. It has a bunch of little things wrong with it... First one I want to fix: When I lock the door, either with the remote, or when it locks automatically after starting, I get a rapid "click click click" type noise coming from the the drivers side door, near the top.... Any ideas? Door lock actuator, if there's such a thing....
Thanks
Also - any suggestions on what I should do first and foremost, like change all fluids, etc...