Ford is having some major spark plug problems. The 5.4 before 2004 is the worst but there are several other engines having the same problem. When the heads were machined the spark plug threads were not cut to the bottom of the hole and this causes a plug to blow out. Usually a tap or in worse cases a heli coil will fix the problem. 99% of the time cranking the engine over will blow out the majority of the material left in the cylinder. Be careful the crud comes out with a lot of force. When Ford corrected the problem they used a plug with 2 pieces and a little too long causing carbon to build up on the end and making the plug almost impossible to remove if left in for the 100K recommended replacement. To remove a stuck plug warm up the engine so the head just feels barely warm to the touch. Spray a penetrating oil, I use sea Foam deep creep do not use WD40, to fill the hole and back out the plug a 1/8 of a turn then let it sit for an hour or so. When removing the plug you may have to turn in and out while applying more chemical. If you do break it off there are several tools available to assist in removal. Be sure you use the newest Ford part as a replacement they are of 3 piece construction. Using anti seize is personal preference but be sure to torque them.