If you decide to pull them just to make sure they don't stick, it might be worthwhile to use a torque wrench while loosening them. On the 4.6 with the plug sticking and falling apart problem, they limit the torque to 35ft/lb, and stop, tighten 1/4 turn, and add more penetrating oil, WD-40, PBBlaster, or ATF/Acetone 50-50 mix and wait. More waiting is good, as it will allow any 'sticky' to get softened by the penetrant, and possibly allow removal of the plugs without them disintegrating and leaving a shell inside... spelled expensive.
Along the same lines, if you are pulling the plugs, and they don't want to come out smoothly, by HAND, (using a socket and extension for access), then I'd throw some penetrant as above on them, and go inside and goof for a 1/2 hour, and then try again. You might just save the aluminum threads on your head by taking your time.
If you get them out successfully, be sure to glop on some anti-seize compound to the next time won't be a problem. Two cents, please.