I did all of the above on my 2003 Workhorse also. The mechanic said the belt was in very poor shape and replaced that but when he got to the hoses he said they were not showing signs of aging and should give no problem. He replaced the thermostat, flushed the cooling system and replaced the Dexcool. On a 450 mile trip last week it worked great but didn't give the cooling system much of a workout because we never needed the AC. We did get to check out the furnace a couple of mornings when it got under 50F.