If it's factory then you should just need to buy a wiring harness for that specific brand of Ford. The harness should take the deck that your installing to the amp.
Check out www.crutchfield.com and go to Outfit My Car.
By the way, you might lose your steering wheel controls when you install the aftermarket deck. I lost my steering wheel controls, but it never bothered me at all.
This is not total wattage.
What RMS is is the continuous power being sent. That's why when purchasing audio, amplifiers, stuff like this, we go off of continuous power because it's what it will always be taking. It will rarely ever hit it's total or maxx wattage.