We have a 3300CK as well, nice camper for a family. When buying used make sure to take a slow methodical walk though to make sure it is to your liking and expectations. Only being a few years old, there shouldn't be too many issues.
As for the hitch, we opted for the Valley 16K Slider. Hooks up easily and with the short box, we wanted the slider for the "just in case" times when you may end up in a tight camp site. Although with the Sundance 88-degree turn radius, I probably won't ever need it.
We had a very similar TV as well (newer 2500hd crew 6.0) but the 3300CK pushes the limits of the 6.0 gasser. So we just upgraded this past Friday to a new diesel as we camp out of state and travel in some hilly regions.
Good luck and happy camping.