The Crossfire gets "Totaled" very easy. Not because it's not built well, but because of how much time and money it takes to replace the damaged parts, and the relative low resale value of the car. It's easier and sometimes cheaper for the Insurance companies to just right it off. In other words, sometimes they really aren't hurt that bad.
If you can find out exactly how bad the car you're looking at was damaged, you could go from that when making your decision to buy it or not.
A $4500 XF that looks, and drives as nice as any other one with that many miles sounds like a bargain.
As long as they aren't trying to sell you a salvage titled car with a "Washed" title, everything sounds like it's on the up and up.
Take it to an independent mechanic and have it checked out before any money changes hands.
Good Luck.