While I was changing the oil in my friend's 2003 Ford Expedition, I took the opportunity to create a guide for replacing any of the bulbs (low beam, high beam, & parking / turn signal) in the headlight assembly.
It should be the same procedure for any 2003 to 2006 Expedition.
Here's the page -
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I hope someone finds it to be useful.Cheers, Paul Michaels Ft. Lauderdale, FL