Yes, easily replaceable and relatively cheap. Remove the door panel (card). There are two sheet metal screws holding the actuator in place. Mark the two hoses and remove the two hoses. If the actuator is the original MBZ part and you know it is defective use a pair of diagonal pliers to carefully cut and remove the white plastic rod holder detaching the lock rod from the actuator (be careful not to cut through the metal lock rod). If your old actuator is as pictured, grasp the plastic collar surrounding the jaws holding the metal rod and push it down towards the actuator body (it may take some force to move the collar downward). Remove the two sheet metal screws and remove the actuator. You may need to use a screwdriver to slightly spread the jaws in order to release the metal rod from the jaws.

On the new actuator make sure the collar surrounding jaws is all the way down against the body of the actuator. Install the actuator so that the jaws surround the metal rod to the appropriate depth of the old actuator (it is OK to spread the jaws slightly for the metal rod to fit). Before installing the screws, grab the collar with two fingers and force it all the way up which will lock the metal rod in place (you will hear a snap when the collar is fully locked in place). Install and tighten the two screws. Install the two hoses in their proper place and you are finished. Test the door lock before replacing the door panel (card).