Level only matters when running the fridge. If it is off, then there is no way to damage it by being out of level.
The reason that you want to be level is the way an absorbsion refer works. The liqud boils, gas rises and condenses to gcool the unit down, then the gas is back in liquid form and drains down the back of the unit. If you are not level then the system will not work properly and you can "Plug" your refer. Sometimes plugging just makes it work poorly, other times it can kill the cooling unit.
Now for a bit of tattling. I make sure I am as close to level front to back as possible, side to side does not seem to have as much of an effect on the operation of the fridge. No more that 1/4 of a bubble out in either direction and I am happy. In my 77 the 6 year old (when I bought it) refer did well for the 2+ years we fulltimed, then we used it for rallies for a year or two, still worked fine. Sold the trailer to my sister in law, and I know they were not as anal as I was in leveling it and within a year they bought a new refer.
WBCCI #5501 AIR # 49
1978 Argosy 28 foot Motorhome
Wise men talk because they have something to say; fools, because they have to say something. -- Plato