Buying a used F-150 with 79,000 miles on it?

A quick check at the NADA site indicates that the price is at top retail. You didn't tell us if it was 4WD but that price is, so if its a 2WD deduct accordingly. My opinion is that, while its not a bargain at that price, if you know the truck's history it could be a decent buy. The biggest single factor on buying used vehicles is knowing how they been maintained, if this one has an established history its worth far more than one off a car lot. Even a VIN check through Car Fax or some other service reveals only issues that have been reported so its not a sure thing.