Um, how are we going to know what's around you? Lol. I see youre in new jersey, but that's a big area too. You really didn't say your location or how far you want your wife to drive.
The dealership is the best and cheapest place. It should be done right, with the right chemicals, by someone who should know what they are doing. (Words chosen on purpose) I have had dealerships use aftermarket universal chemicals. My temper hit red line faster that a two stroke race engine...
Bring it somewhere else and it may not be done right, with the right chemicals resulting it needing to be done again. Worse yet, damage to your cooling system.
Maybe that aftermarket shop has access to Ford's publications and will do it right with the right chemicals more cost effectively.
The other question, do you want it done correctly as ford wants, or a drain and fill? Most aftermarket shops have a coolant "flush" chemical. Who knows what it is or does. Who knows if the shop is using it properly. Then they may have an actual flushing machine that can flush the system backwards. Maybe they just drain and fill. Will they use motorcraft coolant or a universal coolant? VC-1 or a universal flush chemical. Tap water or distilled water? Do you want a new thermostat?
I can't answer your question, but maybe you can ask the shop some questions and determine what is best for you and what you're happy with.
