Trans temp

We are new to camping and purchased a Crossroads 27' Zinger 27RL, we also have a 2010 Chevy Avalanche 1500LT. We went camping last week and pulled the trailer approximately 200 miles and I noticed my trans temp was running between 198 and 205 degrees. We were mostly on flat land as it was on the gulf coast in Alabama. I spoke with 2 guys at 2 Chevy service departments. 1 guy sad as long as the tranny temp did not get hotter than my engine coolant temp we should be ok, the other guy said it was running to hot and if it continued it would burn the tranny up. I also asked both guys about putting another tranny cooler on it and both suggested not to do that. My concern is when I go into the mountains will it run hotter and burn up? Also the truck is rated to pull 8100 lbs, and the trailer is rated at 7850 lbs, I have installed a Reese Weight Distribution Hitch with Sway Control but the trailer dances and porpoises all over the place. I had the trailer set up by camping world and they said everything was right. I was informed by another RV service center that part of my problem was the Avalanche has coil springs and they suggested installing air bags as well. We are now considering purchasing a 2013 Chevy Silverado 1500HD with the all star package on it. We Sally don't want to spend the money on a new truck right now so any suggestions would be appreciated.