Just did NJ to Miami and back in my 2005 with 260K miles on it, and I pretty much just did what you plan on doing, plugs oil... Here's something... When you change the plugs, make sure you look at the old ones. All should appear about the same color and condition. Black is bad, even if they are old. The parts where the electrode is should be the color of tea. This can be a good indicator of impending problems. How's the temp, usually? Maybe a radiator flush?
Good trip, happy Jeeping!