Central Door Locking Actuator - All Questions

Hi, (Re T4 2003) is there a different model for each door or is the central door locking actuator universal?
I am not entirely sure of what I want additionally perhaps. The mechanic pointed to No 1 in the diagram of the locking
mechanism but do I need to buy more to complete what is needed? For example, the part that makes contact with the vehicle when you close the door?
The problem was that the interior pull knobs, both, were going up and down repetitively when I opened the door. A mechanic did a temporary fix saying that a spring had sunk and that was causing the trouble. He said that at some time I would need to get a new locking mechanism on the drivers side door.
I might as well get one for each door while I’m at it. Please can you clarify which parts specifically I’ll need to have replaced as the old ones work for now but they are tired and could cause trouble at any time.