Med Duty tow rig questions

I have a 1999 International 4700 low Pro with the Stalic box. I bought it used in 2002 with 40,000 and it now has 110,000. In all that time and miles I have replaced 1 water pump, 1 relay,a set of batteries, a set of shocks and 1 small gasket to stop a oil leak. It needs tires and they will be replaced in the spring. It has been as close to bullet proof as a truck can be. It has the 4:44 rear axle and the International 530 cube 300 hp with the Allison 6 speed and 22.5 tires. Perfect combo for anyone to drive. It does slow down going up some elevations but that is the way it runs, never over heats and no signs of it wanting to not make it up the mountain. Over all this time the average fuel consumption is 7.5 and most all the driving was towing my 17,500 trailer. When I was full time the truck weighed 14,100 lbs without the 4,400 lb pin weight added.I'm sure now the value is close to nil on a truck of this age and mileage, but at the time it was the truck we needed to safely STOP my rolling house. Most anything would pull that trailer, but stopping was my main concern. It has huge disc hydraulic brakes at all four corners. No air brakes and I know it was an option at the time of build, the previous owner opted not to have them.