Good luck with your RV and I wouldn't worry a whole lot about buying a new WD hitch, they really only help "stabalize" the trailer with the tow vehicle... If you are buying in an attempt to "fix" any issues you have with your tow vehicle - DON'T!!!
Fix what is wrong with your TV or buy a "bigger"? one...
If you have ever seen a vehicle towing a trailer and the back end of the tow vehicle is sagging like it's got a lot of weight in it... that's what a WDH is for. It should help "raise" the back end of the tow vehicle and the front end of the trailer to a more "level" look.
This will help with "sway" because the front tires of the TV (tow vehicle) are not "off the ground".
Ultimately, if this is a serious problem for the TV, you really need to look at what rating your vehicle has for towing, tounge weight, rear suspension condition (did you opt for the "el cheapo" shocks last time?)... If you did go with the "el cheapo" route, that was fine before you started towing something that weighs in at ~4,000lbs+... But now it's not...
If your TV "sags" more than a couple of inches when you hook up the trailer, NO hitch in the world is going to fix what's really wrong, it will just "mask" the real issues...
And make you a hazard on the road for your friends and family and other peoples friends and famiiles...
Your truck should be fine (9300lb limit) and the WDH he gave you should work great. I wouldn't waste my money on a new one if I was you... Just make sure you have a good set of shocks on your truck and check out your suspension and what not on your truck... no broken sway bar links and such...