2004 BMW Z4 convertible top

car is out of warranty, the top has progressively been working slower and slower, now won't work at all, don't even hear the motor trying anymore. the electric latch works but no up or down. using it manually right now by pulling the string in the trunk as mentioned in the information that came with the car. i assume it is the motor, my question is where is the motor or pump, and how difficult to change.

thanks
kp