Many of those aftermarket harnesses, mine included, melted. I bought one from the same place. It melted on a 100* day 150 miles from home, disabling my truck due to overheating. I rebuilt it with bigger wire and 80 amp relays and it melted again. I finally went with what others have done- bought an OEM harness and I haven’t had any more issues. You can get one from a wrecking yard or @ScottyBoy sells them all re- loomed and cleaned up.I’m over 200k also, I don’t think the other components would be worth changing without a known issue. Only thing I might do, as others mentioned, is if driving down the road the ac performance wasn’t what I want, I’d probably start with an evac and recharge to make sure it’s full.
I used a harness from http://www.ls1fans.com/2003__Truck_SUV.php
Junkyard OE fans from a 06 Silverado
Ecm tune from blackbear