top motors

I need to change out the convertible top motor on my 99 E36. The tech manuals all refer to removing the entire drive unit. Is it possible (practical) to remove just the motor by unlocking it from the drive unit, swinging it down, and then just replacing to motor itself? If so, can it be done with the top fully up, or down? Is it necessary to have the top in the half-up position that the manuals refer to when removing the entire drive unit?