I opened the gearbox and what u said is correct.
Diassembling was easy. Just undo the scerws that holds it apart, after releasing the spring.
Note, to seperate the two parts you will have to use a solder iron on the motor attacments, because the wireing is wery tight.
Assembel however was more difficult. Gears alignment, microswitc etc.
But it is only the third time I do a Gearbox. I think a "pro" will have no problems at all
And I am not happy having to do this on a new gun at that prize.
But when you buy overseas.... HK doesent do guaranties/ warranties.