I am getting ready to purchase a used Tahoe. Between 2011-2013. I will be towing approx. 6000 lbs a couple times a year up and down bigs hills. The vehicles I am looking at has a hitch and a towing control on the shifter. The salesman is telling me that is has the towing package but no tranny cooler or anything mechanical. Is this correct? And do I even need any of that?