The v6 in the Sedona 2003 and similar years (and as a matter of fact a lot of cars with v6) have 3 plugs on one side that a completely covered by the plenum (air intake). It's a very big job time wise and some of the rear attachment bolts are near impossilbe to get at without the right tools and/or knowhow. The job is about $325 in my area without wires, which is BS because you need to do it. The job is too big to risk a wire going on you a few 10's of thousand miles later. I believe the dealer book time on that job is 2.5 hours. If you are a weekend joe blow car guy, like myself, give yourself 3 to 4 hours because nothing usually goes smoothly. I have very detailed instructions on how to do the job. Pictures and all. See the link I added as a source for the above info, but read the info below first.
If you are having misfires before the life of the plug should have been over listen and watch the engine with the engine cover off and look for arcing from the coil over plug unit that happens in conjunction with the misfire. I clearly saw mine during the day but the darker the better. Around $109 for part. Look for the arc especially around the mounts that support the holders for the plug cable wires. The unit may be arcing to it. Let the car get nice and hot before looking. that seems the best time. parts store who sold me the coil told me he sold 50 last year and is now over 100 this years. These things are dropping like flies.