Here is my take on the HPO change. Is it necessary, probably not. But if you buy a used 7.3, i would probably change it out, because you never know how the previous owner maintained the truck. if someone neglected their oil changes and didnt change it regularly, then i could see how the oil could be sludged up.

It isnt a bad idea to change it out, but if u do it once, there probably is bno reason to do again if you keep regular oil change intervals.