Agree with Phenom on the hitch arrangement. We own a 2005 GMC Sierra 2500HD Duramax and have the B&W Patriot 18K hitch. The hitch is set to 4" to the rear of the axle. We have over 2,000 miles towing with this set up and have had no trouble in backing the rig into a spot.
We have owned a Curt Q20 slider before and found that we hardly ever used the slider function. The Curt had a lot of play in it and that caused some noise issues when stopping/starting. The Patriot is much tighter and gives us more confidence when towing. Patriot is a piece of cake to couple/de-couple: a good solid hitch.
The GMC has been a great truck: 4WD, short bed SLT package. We added an after market exhaust brake (Pac Brake) which helps slow things down, however it is a gradual process due to the weight of the 5er pushing us. Unloaded, she slows it down like I'm braking with heavy foot pressure. Additionally, we don't have to buy DEF, which saves us money. We're planning on keeping our GMC until we're done rv'ing.
Good luck with your new truck, moose074! Happy camping too!