The 5.4L 3 valve engine is a wonderful engine. But those two piece crimped together plugs was an awful idea. The same plug is now available in a two-piece-but welded variant.
I have had them changed and didn't break any off in the process.
1. About 1 week before the change, put about 4 cans of SeaFoam in the tank.
2. Run the tank to about 1/8 empty, put in 2 more cans!
3. Have your mechanic do fuel system flush with even more seafoam direct into the manifold, or what ever he chooses to finish de-carbonizing the engine. We are trying to remove carbon deposits from the plugs.
4. Remove all the coil packs. (This is a good time to clean the contact on the bottom, as they tend to corrode. Take your time and get them really clean.)
5. Loosen each sparkplug, Don't force any thing. Now pour a little seafoam into each spark plug hole. The point here is to soften any remaining carbon on the plug.
6. Let the engine sit/soak over night.
7. Gently back out each plug. If it binds up, loosen and soak some more.
Using this method we changed all 8 at 93,000 miles without breaking one.
Once the new plugs are in, take it for a good romp to blow out all the excess seafoam. Then got your oil changed, preferably the same day as it will be contaminated with seafoam, if you dumped all of it that you should have into the sparkplug holes.
Don't get fancy overpriced plugs. Go back with standard-but-new-one-piece Motorcraft plugs. They are cheap and that's what Ford engineers said put in there. You will want new boots as well. A little anti-seize going back helps out the next time.
I also run factory style oil filters and Motorcraft semi-synthetic engine oil. Walmart has the oil and the Seafoam. Gumout makes a similar product.