Solved. I received the deep socket from SnapOn last night. I went out to remove the stripped plug and the new socket couldn't grab threads right away. I used a tool to slap the extension down harder onto the plug. It caught and I removed the old plug w/o much difficulty. When I went to put the new plug in, I discovered I couldn't really tighten it! I was beginning to think maybe the threads in the head had given out. Long story short: Deep at the bottom of the spark plug well, there was a buildup of hardened brown crud. This prevented any socket from seating fully home on the plug. Using a thin kitchen knife, I scraped the area over and over. I used the can of air to spray all the debris out. Finally, I was able to seat a socket onto the plug and torque it to spec. (13 foot lbs or 156 inch lbs.) Gave it a test drive and it seems good to go. Thanks for all the suggestions.