[Rick 427 Cobra]

Not all spark plug inserts are Heli-coils. Heli-coil is a brand name of a particlular style, a stainless coil with a patented locking arrangement. Other styles are usually little more than a threaded sleeve which, if not done properly, can easily remain on the plug when removed. I can not imagine a true heli-coil coming out without total destruction.
Regardless of the insert or head material, as Roscoe says, use anti-sieze
If there are still good threads in the head you can usually just reinsert the thread-sert kind.
Rick