Winne calls it a Year 2000. They can do that even though the chassis might be a 1999 Ford. Very often, the Chassis Year doesn't matter much. But 1999 to 2000 in Ford E-Series was a change to "Performance Improved" cylinder heads that raised HP from 275 to 305 and addressed a spark plug issue.
31C is one of my favorite floor plans. I don't know if all of them have an interior "step up" toward the rear. Wouldn't bother me, DW wouldn't want that. It's become popular, by the way, adopted by Forest River in some of their C's.
It can be Leak Tested with a Seal-Tech or other (even home made) pressure tester. Has essentially a furnace blower to apply pressure inside the coach. Then the tester sprays all exterior joints and seams with a bubble solution.
Not built for offroading. You don't want to rack the coach with a twisting motion. Probably get stuck in anything soft/sandy/muddy/wet, even deep gravel. There will be well over a ton on each of the front wheels.