The vac motors are some of the easiest to change i've come across,
You can change either motor in 10 min's easily, Perfect heat coils have QD's either end and come out together. Try changing number 1 motor on an old Woodbridge machine, that was much more of a fiddle, same applies to Ninja.
If you turn off the valve, you by-pass the Perfect heat system, (no preheat) not the heater.
Just read the manual it does say by-passes all the heating system, but in 2 years i've never turned it off.