I live just south of Erie, and last year used 6 to get out to the kinzua dam. The road is decent the whole way. I also have a 31' Airstream, and I didn't have any problems. They have some really nice boondocking sites if you're interested in that...the park service refers to it as dispersed camping, but the sites are great as long as you're not afraid to tow down a road wide enough for 1 1/2 cars! There are a few that are really easy to get in and out of. The national campgrounds along the river aren't too bad, they don't have utilites available, which is the only draw back. There is a nice park just off 6 before warren with electric hook ups and nice shower areas (the Buckaloons), and then one just past warren with electric as well (Chapman Dam). I drove out to the PA Grand Caynon a few years ago with no trailer, it was a good ride, you should be ok with the Airstream. I'm not sure of the parks out there they should be state parks. If you go to Pa. Dept. of Conservation and Natural Resources
they have all the state campgrounds listed and all the information is there and Allegheny National Forest - Welcome!
has all the information about the allegheny forest. I would not stay at the Tracy Ridge Campground, it would be too difficult to get in there. Red Bridge was closed this summer for work (I think they added electric) It should be open this year. If you need any let me know! Enjoy your trip!