I was thinking about using C.... the only problem is I need to check to see if they have a loaner car, where as if I use dealer A they could drop me off at work. I'm just wondering if dealer A is using high school kids and they are being supervise by a certified technician.

From what I know the two piece plugs are pressed together with the ceramic and electrode as one part and the threads and nut as the second part. Somebody chime in if I have this wrong. What is happening is that carbon is building up on the elctrode of these super long plugs and basically when you unscrew them the center portion remains in the head while the threads and nut come out. Again I could be wrong on the exact details of this but it is something close to this.