durango tranmission cooler

I currently have a jeep liberty and was driving down hill (sierra nevada) in the rain with my 2720 in tow. On a curve it was really pushing me. Enough so, that I went to the dodge dealer and looked at durangos, they have great deals on the last few 2006 models. None have a tow package, he told me they can hitch and wire it for 650 dollars. I asked about the transmission cooler, he said they already put it in all durangos with airconditioning. Any input?