since there is no official off road difficulty zone rating system there is no real answer. Most parks will give an idea like "To ride these trails it is suggested to have X size tires" Then some will say 1 locker or 2 lockers, winch, body protection, ect. I dont see any info like that on D-towns park but I linked the map and enlarged in Adobe and looks like zone1 is easy, zone5 is hard just by the obstacle names. Zone1 list 1 obstacle called Jaw Breaker which looks like small rocks yet zone5 has names like Ballbuster, Cougar Canyon and Nut Cracker. But I am not sure on that so we will have to ask once there.
One thing I did notice is it looks like the trails are directional. There are arrows on the map and one trail says 2 way traffic next to it. Can someone who has been confirm this? Not a bad idea to keep traffic down.