I have seen the NT's apart and if memory serves, you need to seperate the stator from the motor. The rotor is threaded onto the output shaft of the motor. Sorry, no info on right or left threads..but it should be counter to eng rotation. This is a delicate deal...be very careful not to damage the windings or you will trash the whole deal.
Removing the shaft will require about 95% of the engine to be taken down, so yes, he flywheel and most everything will come off. About the only thing left whole will be the block.
The job isn't for the faint of heart, that's for sure. I had to take mine down for a shaft swap. Seems Miller is the only one my particular shaft was made for. I was busy at the time and had a Onan dealer do it. Cost me over 700 bucks at 65/hr!