Mine arrives today too! From pinside to avoid it breaking.....
"Definitely take it apart before installing. Three major things to check.
1) That the roller on the motor shaft is positioned correctly and that the set screw is tight. There is a great detailed post in this thread on how to check. This can cause the head not spinning/grinding issue.
2) Make sure the strap clamp holding the motor steady is tight. If it starts rotating in that clamp it can short on some screws and blowout the motor control board. This can be the cause of the head not spinning/grinding issue, and then the head not moving at all issue. At this point also check the motor position. The shaft is offset, the motor should be positioned so the roller is against the ring that rotates the head, but not so tight against it that the motor is leaning in the bracket. This is important especially if you tried out the topper and already had the motor rotating issue.
3) Check that none of the flasher lamp sockets are contacting or close to contacting the metal cover, can cause lighting issues.
All in all you are looking at about 15 mins of prevention to save a lot of potential headaches.