Usually those actuators are riveted in to the side of the door, or
perhaps in the door panel. You have to drill out the rivets to remove
it. Then use regular nuts and bolts to put in the new one.
I'm not sure what you mean about the black and silver thing. That might
be the actual motor for the actuator.
To test the actuator, remove the electrical connector and put a
voltmeter ,or 12v test light on it and hit the door lock switch. If you
are gettting voltage, then the actuator is bad.