My 2010 will be passing 90,000 miles tomorrow. I've kept up with all of the maintainience on it and have had zero issues with the power train. The only problem that just surfaced is a bad blend air motor which I'll be fixing shortly. After some research it looks like a fairly common F150 problem. Have a mechanic look at it if you don't trust your own judgement. Don't forget to look at the front and rear shocks for fluid leakage. With that amount of miles the shocks may need to be rebuilt or replaced. I rebuilt my shocks at 65,000 miles.
As long as everything checks out mechanically, buy it and have fun wiping the smile from your face!