No thread locker.
And most people get the best results with simple copper core plugs, not platinums or iridiums (although the previous poster did use them). Because the plugs are easy to change every 30,000 miles in our KK's, there is no need for an expensive plug. Copper has the best conduction characteristics of any metal but wears down faster than platinum, etc., hence the 30,000 mile change interval.
Even thought my rig was running ok, I pulled the trigger and had the steelership replace my plugs at 105k. I did ask for the "parts" to be returned but the tech who did the work not only didn't return my parts, SHE failed to put the intake pipe back on after a throttle body fix. Now, I wouldn't normally make too big a deal out the pipe being left off the air intake (engine side), but this the 2nd time this dealership has done this. Once on my 2011 minivan. Drove around a week with it sounding like a had a holly 4 barrel with the breather turned upside down. Sent a pic to the service manger, he called to apologize. Thats as far as it went. He11, had he offered me a half off car detailing, I'd not be so ticked about it..
Oh but he did say my plugs were bad but he's seen worse w/less miles.