Spark Plug Change in a Truck--How Hard Can it Be? Update#2

Wanted to see if I could get one plug out and put it back in. I was able to get the top part of an ignition wire off easily but the bottom end goes in a metal tube and that all wobbles where it goes in. How do you get that off the plug? What's with the metal tube?

Only obstacle seems to be at the front left plug which is behind a plate sticking out from the alternator. Looks easy to remove that temporarily.