The CTIS fitting on a stock setup looks like this:
Unlike most other air type fittings, all this fitting does when you trip it is disconnects the tire from the rest of the air pathway.
You then unscrew the entire assembly off of the spindle. You don't remove the tube from the spindle, you literally unscrew the entire assembly off of it.
Another set of directions can be found here:
http://www.humvee.net/hid/tire/changing.html