Spark plug problems.

Well finally came time to replace plugs and guess what. The idiots at crown bmw in Greensboro Nc scored again. Seems like the last time this vehicle had the plugs replaced they only replaced 5 instead of six. They stripped the threads on the plug. What besides taking it to the dealer can be done to pull the plug out. Is there a specialty tool for this .
Thanks in advance for any help with this problem.