Your going to want to change those plugs at 48k. At least the top ones. The bottom ones are platinum. The earlier single plug 3.7/4.7 engines would wear the plugs down into the porcelain at 40k. The later duel plug engines do a little better but not much.
Your going to need a very thin wall socket. The only one I found that fit was one from snap-on.
Don't be surprised if the spark plug boot sticks to the plug and tears off. You can buy those separate from the coil if you do.
Make sure you use some dielectric grease on the boots when reassembled.