oh and for reference the ATC teardown thread is this one :
viewtopic.php?t=5333
however I do have one slight correction. he says you don't need to remove the heatsink to remove the motor and gearbox..... you do
its held with 2 small grub screws in the solid band at 12 O'clock and 3 O'clock facing the ATC. if you look in the photo of it disassembled you can see the top grub screw and corresponding witness mark on the top of the motor. you need to remove the heatsink to get at the screws holding the motor.
he does say he cant remember doing it but it does need to come off.