I'm wondering how it is that on a spark plug replacement job, the estimate for parts is between $71 & $156? Am I missing something or does that price for parts seem inflated?

The pricing varies due to the various part qualities and brands available for use. A set of original equipment spark plugs from Ford could cost even more than the range listed. Also, be advised when you replace spark plugs on this vehicle, you simply must replace the rubber coil boots that fit over them. If not, you will be inviting a sure engine misfire.