A couple of my favorite campground locators:
http://www.epgsoft.com/CampgroundMap/
http://www.ultimatecampgrounds.com/uc/index.php
No experience with the ovens, but make sure you use them outside due to both carbon monoxide and fire danger.
Regarding propane, you should get at least 2 weeks, maybe a month on just cooking and the fridge. Using the furnace would cut that down to just a few days, a week on the outside, depending on how much you use it. The furnace fan will also be your #1 electricity draw if you're on battery, so watch that. If you can find a campground with electrical service, get a small electric box heater and use it.
Although from experience a heater in a popup is almost futile. Makes a great hand and foot warmer and might warm it up a couple of degrees to take the edge off, but it'll never be shirtsleeves in freezing weather.
