To add to Wayne's info above, who added to mine...

That is exactly it. Carfax is only one tool. Any competent mechanic should be able to tell if a vehicle has has serious crash damage. There is not a body shop out there that can make it perfect without leaving some sort of superficial clue that work has been done. Heck you can do it if you know what to look for.

It is ultimately up to the buyer to inspect or have the vehicle inspected.

Insofar as Carfax being "incomplete" that is not quite true, or not quite fair to Carfax. They are limited by the information and databases they have. This includes the age of the data, how a state codes things and even if/when/how a car is considered to be totalled/salvaged/ect. For what they charge, I think they provide exactly that amount of value. I know I would not want to spend my time researching the title history of a used vehicle (it is possible as all the info is public record).

To bring it slightly back onto track here, just get the vehicle looked over (if it makes you feel better), change the oil and drive it. A dealership is not needed, if you have a mechanic you usually visit.

Good Luck,
Michael