Put a remote thermometer in the belly so you can watch the temps. You will find you are good down to about 28* if the wind isn't blowing. Below that, the belly will get to freezing temps over night.
However, you don't need to winterize. Just put an electric heater in so you can keep the temp inside about 50*. Won't need to run much, but will provide enough radiant heat to the basement to protect your lines. If it gets real cold or strong winds, you may need to let furnace a little to put heat in the basement.
If you can keep it on the truck, the truck bed keeps the wind off and adds a bit of insulation which helps a lot.
That far north, you may not gain all winter, but sure will gain a few months of non-winterized use.
Down here in SC, I only rely on the furnace since mine is in a storage yard. Only when it gets down in the low teens do I throw it on the truck for the couple days we have temps like that. Down to 20*, the battery is good for about 5 days before I use to bring it home for a recharge. But with a new 100W solar install, I hope the battery will be good all winter. Also only use about on 20# tank. Six winters and I've never winterized nor had issues, despite seeing multiple days with highs about 30* and lows in the teens.
