Mine is a 2001 F350 with 155,000 miles. I've owned it for almost a year. To get it ready for this camping season I flushed tranny, transfer case,front & rear differentials and replaced them with Mobil 1 synthetic fluids. So far I've installed the 6.0 cooler, MBRP 5" exhaust, S&B intake, and Autometer gauges(boost,pyro,trans temp). I'm ordering a DpTuner F5 Chip tomorrow. Everyone i have talked to say it is like driving a new truck. I know what you mean about these trucks being a little sluggish on hills. My trailer is around 8000lbs fully loaded. I have read up on DpTuner and that is who I decided to go with. They have specific tunes for towing,daily driving and racing. Call them and tell them what your looking for and they will hook you up....
http://www.dp-tuner.com/