From my understanding the 2004 and early 2005 5.4s had some problems the later ones did not. What it the cutoff date for when these problems were addressed? According to the sticker on my doorframe, my truck was built in July of 2005.

 

There are several POTENTIAL problems in the period that you mentioned. The '05 has injector problems that could be catastrophic if an injector sticks open, although there is an extended warranty on the injectors and any RESULTING damage for 11 years and (I believe) 120k mi as a result of Ford being sued.
The spark plugs CAN break off in the head when removal is attempted, do your homework BEFORE attempting removal. That problem was corrected in the '08 model years with a redesigned head and spark plug. There are other problems in that time period, but each have different correction dates.