My experience has been customers scream bloody murder if they have to pay for things that weren't needed. Most guys on here would and most would say find a different mechanic,sounds like he doesn't know what he's doing. On your own truck as Hobbie great change all the things you want,I still don't agree with it. Seriously many O.E. parts if they test good are better quality than the aftermarket replacement parts. Example an original TBI fuel pump would go for years,it dies,you put in an aftermarket pump from advance,O'Reilly, any discount parts store.Now you're changing them every 2 years or less. When I worked at Pat's shop we wouldn't install parts store pumps on FI cars.
And the guys that beat book,spend a lot of money on tools,and they diagnose.They diagnose quickly and fix the car right the first time and change only what's necessary. Any unnecessary steps cost me money.
I'm not trying to start a war,some guys like fat girls,some guys like skinny girls. It's your life,your truck and whatever makes you feel best is what's important.