[dutchmensport]

No two places in the camper will be "level" at the same time. So, find the spot that is most important to be level and use that.

I like to use the entry door frame. Using a carpenter's level and using the door jam I can measure "level" front to back and side to side. If the door frame is level, the rest of the camper will be also.

About releveling. Ideally, you need to hitch up pull the trailer forward or backward and put something under the tires to get it level side-to-side. The wider and longer foot print under the tires the better to keep the tires from sinking.

Ideally, this is the best way to do it. More than likely, being a little off level will not hurt anything. A LOT off level will.... namely, the refrigerator.

If you can handle your eggs rolling to the edge of the frying pan every time you fix them, then being slightly off level won't hurt anything.