Finally manned up and got a AOW

Bought a SIG MPX

GREAT experience at Range 129... A few questions.

1. Can I change the muzzle break
2. Can I use a blast can? ( Warden)
3. Can I change the Brace to another brace? As long as its a brace?
4. Do I have to notify NJSP I have applies for a NFA item?

THANKS