I can't speak for the State Park, we didn't stay there. We stayed at River Falls at the Gorge Campground and that had a steep hill heading down to the river, not bad though. We made that climb out with our 38' fifth wheel just fine but is was a little intimidating. :B
If I remember correctly we did check out the state park, the sites looked very nice BUT I can't remember the drive in or out of it, sorry. :h
I can say though that the gorge itself is beautiful!! Definitely worth visiting at least once!!! Good luck with your trip.
Dan