Which dealer, trailer or truck?
Just guessing, it is the trailer dealer, and it's likely you might not need either, given the truck capacity and the size of the trailer.
One important detail to stay on top of, regardless of whether you go for those parts, is tire pressure. A Pickup truck, empty, is going to handle best with lower tire pressures, particularly in the rear, than will be needed when you load it up. Too much air in the rear tires when empty makes them ride hard and bouncy. Load the truck up, however, and too little air will make the truck directionally unstable. It'll be squirrely and you might really need the entire roadway.
With a 3300 lb dry trailer, you are probably looking at 5,000 lbs or so loaded to go camping. This is well within the 9,000 lbs capacity for the truck, and adding the 500-600 lbs tongue weight to the back should be fine. But you will know for sure the first time a semi passes you on the interstate. If you need a sway bar, it'll be because the semi blows you all over the road. If you need a WDH, it'll be because the rear of the truck sags when you hook up the trailer.
My guess is that you won't need either. But you are the one who has to make the call.
