In looking at the trail level descriptions, it looks like the trails are variations of what would normally be a Green coded trail, with the hardest trails ("Difficult") being what would normally be considered a Blue coded trail. Some Blues typically also would require skid plates in addition to sliders, but not all. A Black would be the next step up, which would add a locker to the armor, etc....with some blacks needing 35's, but not all, and so forth.
So, if you've wheeled before and have 33's and sliders (Everyone should have recovery points and gear, regardless of level...), it sounds like you'd want to only do what they describe as "Difficult".
If built enough, but new to wheeling, or, experienced, but bone stock, the other trails sound like they'd be good for learning the ropes/keeping purdy.