I had the exact same problem on my wife's car not too long ago. Reference the following thread for the fix:

Spark Plug Thread Repair

Skip to the bottom of the thread for the instructions.

If that thread doesn't answer your questions, let me know.

Good luck!

1996 Ford Contour SE (Mine): V-6 MTX/DMD/MSDS/K&N3530/Torsen/Spec-1/Split-Exhaust/Walbro/Syncromax..119K 2003 GMC Yukon XL SLT (Hers): 285HP/Stock..93K