Get some penetrating oil ....warm engine.
Get some JB Blaster penetrating oil (any autoparts store...) and spray the base of the plugs when the motor is warmed up. Let it sit in there for a few minutes and remove the plugs. If they're binding try working them each direction to free up the threads and let more JB soak in. When you re-install them use a quality 3/8" torque wrench and only torque them to specs, don't over torque 'em. If the threads come out of the head you can always use Helicoil inserts to repair them, that's what most shops would do. But you should be alright. Also if you have an electric impact driver the vibration from the impact driver helps free up the stuck plugs too without damaging the head threads.