Thinking about the situation a bit . . . sharing my understanding of diesel fueled vehicles . . . it seems there's two likely scenarios:
1. The misfueling was noticed during the process of adding gasoline, via the gas can to the diesel fuel tank, and the truck had not run at all with gasoline in the fuel tank.
2. The misfueling was noticed while driving the truck to the station to fill the tank with fuel because the truck ran rough or stopped running.
IF it's scenario #1, then dropping the fuel tank, draining it completely, and refilling with diesel fuel would be required. Also, changing the fuel filters and flushing the fuel lines would be prudent.
IF it's scenario #2, then explicit instructions from Ford would be a good idea for resolving the misfueling. Seems likely the resolution would, in addition to replacing fuel filters and flushing lines, be replacing the high-pressure fuel pump, the injectors, and perhaps the high pressure fuel lines. And, with this scenario, there may be diagnostic instructions in an effort to see if the engine was damaged. Perhaps a compression check of all cylinders would be appropriate.