If you want to buy new, you can get them cheap at SparkPlugs.com
Or you could gap them down a little to make up for the wear. Just make sure to gap them gently since the heat of combustion will weaken the ground strap, and make sure you don't gap them too much, then bend the gap back open again. Weakened ground straps can break off if their regapped too much.
I'd use the iridium if that's what's recommended by the manufacturer. I've heard of people using regular copper core plugs in cars that were designed for platinum, then they complain because of poor gas mileage.
They spark easier electrically speaking than standard plugs because of the higher e-field on the smaller point area of the center electrode thus they if ignite fuel better under lean and high pressure conditions. Money well spent!