Well, there should already be holes drilled in the frame to accommodate a frame mounted hitch. That's what they include from the factory if you have the basic "tow package"..
In other words, it should already have a 2" square hitch that looks something like this.
Plus, you will need the big 7 pin electric plugin to the trailer for the electric trailer brakes...
When it's all said and done, at the minimum, it should look like this with the WD bars attached and all.
Do you have a brake controller?
On edit, the "tow/haul" button does not add any more "power"... It only changes how the trans shifts. In other words, it will make the engine rev more to get into it's power band, so expect some 3000+ rpms at times.. ;)
Mitch