The general rule of thumb is if you're comfortable walking in the rig, you're level enough. My Norcold manual says 3 degrees side to side and 6 degrees front to rear. Remember, on absorption fridges the freezer cools first, then the box. I'd put a thermometer in the freezer and see what it's doing.
Above is the simple answer. Since you're getting ready for a trip, you might want to verify the fridge is operating at all. To do so, you'll need to provide the brand and model number of your fridge. If Norcold, has the recall been done? Is the red light on? Do you see any codes on the eyebrow? Provide more information..there's lots of smart people on this forum.....Dennis