I have a driver's license & I have no problem driving anything from a Corolla to an Explorer. But if I climb up into a semi truck, I'm not going to get out of the parking lot. Those big rigs take an entirely different license to operate.
You can put a HVX200 into PhD mode (Press-Here-Dummy) & anyone who has used a handy cam can use a HVX. That isn't the case with a HDX900, that camera is in the big rig category which needs an entirely different license to operate.
If you've ever shot with a Betacam, you'll know prettymuch where everything crucial is is on the HDX900. If you haven't you'll need to find someone to teach you, online forums aren't going to do you enough justice.