Couple options. Need to run CPAP can be done with 12v power direct in many cases. You need to check with your CPAP manufacturer if the proper adapter is available. Then you just need to get 12v power to where it is needed.
Or you can install a small sine wave inverter and plug into the closest 120v outlet.
Either way I recommend 2 to 4 batteries to keep the power on without worry.
Your RV dealer should be able to help you get this done if you are not mechanically inclined. Please post what the estimate says they are going to do so you know you are getting what you need. Not more, not less.
I am not fond of generators but another option is to run a Honda 2000 all night.
Here is some reading for being off-grid:
The 12 Volt Side of Life