Although I wouldn't normally DARE disagree with wiswind, I would add that Ford does not manufacture their O² sensors. They are sourced externally. If you open the Motorcraft box and see the familiar Bosch part number sequence on the "Motorcraft" sensor (in addition to the Ford part number), don't be too shocked.
That said, be very careful about your replacements. Using an aftermarket (Bosch) sensor has never been a problem for me, but IF you decide to do this, avoid the "universal" sensors and get the Bosch sensor designed as an "exact fit" OEM replacement. It is more likely to have the correct fluting on the sensor tip, correct tip reach into the gas stream, and proper lead length and connector. The connector is less of an issue for sensor performance and more of a convenience, but the tip length and fluting on the protective cap can be critical.
You might also want to get a supply of antiseize compound to apply to the sensor threads when you install, since the little dab of compound that is usually applied to the sensors as purchased is seldom enough. Just make sure you keep the compound off the sensor tip.