They make a tool for pulling the broken plug. Tip for future removal is to use an impact gun to break them loose. Never broken one myself.
As far a removing the head the worst part would be removing the intake manifold. They have a stupid vacuum hose on the back of the manifold that is terrible to get access too along with some actuator arms for something.
If it's the 3v I've broken a ton of them at work. Enough between the three of us we wore out the Lisle tool and had to buy a new one, but it's never let us down. It doesn't matter to me if it breaks or not cause it only takes me less than 5 minutes to pull them with the tool.
If you're talking a 2v motor I can't help you, never seen one of them break a plug, but I've fixed a bunch that blew the plug out.