Hi Red, welcome to the forum. Plenty of good info here.
Your existing vent fan runs on 12 volts, so that wiring will be of no use for the AC.
A couple of things you can do is to look in your breaker panel for a breaker that is marked "Front A/C-20". It will be a 20 amp breaker.
The other thing to do is remove the interior shroud on the existing fan and look around for a yellow cable that terminates in a plastic box.
If you have these, then your are wired for a second A/C.
Or one other thing to do is call Heartland Customer service with your VIN in hand and they will be able to tell if you are wired for A/C.
Peace
Dave