My buddy has an 02 f150 Screw 2wd and after a day of mudding he had a code that came up cyl 8 misfire. I assume its the coil but what else could it be? And what needs to v6 e removed to change cyl 8 coil? Looks like fuel rail is in the way.
Chances are that the spark plug hole got water in it and is causing the problem. You can take the coil out with out removing the fuel rail, just rotate it. Don't pull the plug until you are sure the hole is free of water.