I replaced mine plugs as soon as I got my 06 f150 5.4. it had 43K mi on it. They key to help you have them not break is to have the engine warm. Not hot, don't burn yourself. Having it warm/heated up will help the aluminum to expand, thus not holding the plug so tight that it breaks. Hopefully there isn't too much carbon on the bottom end of the plugs. Then you can do what i did...replace the plugs with the OE champion plugs. Made for the 2004-08 5.4 f150, but it those are a once piece plug, so they won't break the next time you change them out. Hope this helps.
-Charles

 

Just hope they were changed once already. I changed mine in my 05 90,000 original plugs loosened each plug a tad and used aero kroil to soak them overnight. I used hand tools and worked each plug back and forth. I only broke one of course the back passenger plug but Lisle tool works like a champ. My cousins 06 we warmed the motor up and used hand tools working each plug back and forth all came out (think they were changed once). Its a crap shoot, just have some luck on your side and take your time. Good luck and buy the Lisle tool if you decide to do it yourself.

 

Why is the 5.4 such a difficult one to replace anyways? And can someone sum up the purpose of a spark plug? I know they basically create a spark in the engine but is that just for start up or continuously while its on?

 

The tip fires a spark that causes the gas and oxygen in the cylinder to explode.

 

The 5.4 3 valve uses 2 piece plugs that like to stick in the head and break when you try to remove them.

They have to fire constantly for the engine to run, except in a diesel. Diesels don't have them, they have glow plugs to get it started, then it's self-combusting.