I test drove a 06 f350 with 133 thousand miles and after test driving it would not start back they said it had a high pressure oil leak and fixed it is this common and what would it cost to fix if it happens again?

 

High pressure oil leaks, sadly are common. I did the stand pipes and dummy plug's in my truck for around 140$, and 8hours of my time. (A tech can do it in half that time) The STC (Snap To Connect) fitting, I hear is about 700-1200$ to have a garage install. This being said, the new part's are upgraded, and once completed, you should have no more issue with the Hpop system leaking.