I'm not sure I really understand, but after reading the problem a couple of times I think I get it. Oh, now after saying that, I'm not sure again. Here is what may work. You can buy what's called an 'Easy Out' from most auto type stores, I'm sure Sear's would carry them. If there is a hole now straight thru what's left of the spark plug body inside the cylinder head threads, you may be able to tap the easy out into the hole then use a crescent wrench, or an open end wrench and turn out what remains of the plug. Then if you think you still have debris inside the cylinder, turn the engine over by hand to TDC and rig up a straw on the end of a shop vac and vacuum out the spark plug hole and the top of the piston. But, if just the threaded body of the old spark plug remains in the cylinder head I'm not sure you would have any contamination inside, yet.