Before you do anything, check the sway bar bushings to make sure they aren't worn out. My coach was doing the same thing when I first got it and after someone telling me to check the bushings, I found that the front two were basically gone and the rear had lot's of play in them. Either way, you'd do yourself a good day's work by replacing the existing ones with the poly sway bar bushings. These are the ones I used and I think many on here have too.
Poly Sway Bar BushingsAfter you have replaced those, you can start looking for other helpers. Make sure your tires are properly inflated for the weight you are carrying. Although I have not done it yet, the Cheap Handling Fix seems to work for most folks. I just installed air bags on my front end, which made a SIGNIFICANT improvement in handling, and will be installing them on the rear when I get time. The other thing that I found out was my king pins on the front are slightly worn....not to the point of a safety problem, but beginning to get wear to the point where a heavy truck alignment tech says it wouldn't hold the alignment for long so he wouldn't do the job. For now, I'm keeping the grease zerks full and I don't get the wandering feeling that I had before.
Then there are the steering stabilizers and the trac bars that all contribute to better handling and ride. Lots of tools and toys that can take your money and offer varying degrees of improvements. Get the basics of the suspension taken care of first, and you may not need anything else.