Carfax is not magic. It is just a database of where it has been titled and when that title transferred. Part of their sales pitch is to make it sound like they can find "bad" things. Those things are transfers, or information mismatches. Things like mainteince do not get registered anywhere. Heck, unless it was deemed totaled by insurance and reported to the state, even massive repair work won't show up. Body shops are under no obligation to report what they repair as long as someone is paying for it.

Don't get me wrong, I used Carfax heavily when I bought my last truck. But I was looking for things like vehicles that had done the auction circuit. When a vehicle travels from the east coast, has 3 transfers in as many months you know something is not kosher with the vehicles. Fleet vehicles are often suspect, but if it was just a rental it is better than something that was used in a work/business fleet.

As for having a mechanic look at it, you could. Although, that should have been done before you bought it as any problems now are wholly owned by you. A dealer may be able to pull information regarding recalls if they are nice. But, remember it is a 12yo truck and you have to take that into consideration with anything you find.

Beyond that, if it seems like a good truck just enjoy it and drive it.

Good Luck,
Michael