It's probably just the coil.
Iirc 8 is located on the drivers side all the way in back. You have to remove a bracket by the pcv and then 2 bolts holding the cop cover on. Unplug #8 coil and pull it out.
If you replace the plug..
At that point you'll have access to the plug. Remove the plug when the motor is stone cold, you do that so that it'll be less likely to strip.
Insert new plug carefully, remember that it only has about 4 full threads to catch. Most choose to put them in dry (w/o antiseize). From there just lightly coat the inside of the new cop boot with die-electric grease and slip it on.