I haven't had a chance to talk with Gus, the mechanic, since his recommendation. He was going to run some prices and give me a quote, probably Thursday. As far as what the glow plug is doing, the threads did not come out at all. The plug sits as if it were still set in the head, and is just spinning freely clockwise and counter-clockwise when force from a socket is applied.

I did find it a little strange that the shop did not even mention the possibility of drilling out the glow plug, and jumped immediately to a new cylinder head. Either way, the car does have 200k miles so I would like to try to fix a few things inside such as having the valves redone as recommended by most of you.

I did get in touch with the individual in CT about the cylinder head (thank you sixto) and I would be able to have it shipped to Colorado Springs for ~600. I'll keep you all updated as things happen, and thanks again for all of your help.