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Taken from my 2007, also 1st gen, service manual. From what you described, sounds like the antenna rings is loose, probably from plastic retaining tabs being brittle and snapping. Replacing that part doesn't look all that hard. But until you go in there and inspect what's broken you don't know for sure it's the ring part rather than the fixed mount.
Step #3 looks intimidating, but I read each substep and they're not hard and only need standard flat and Philips screwdrivers. Of course, about 1/3 of the pushpins will snap given the age of the vehicle, but you can likely get by by judiciously spreading around the pins that are still good - it usually works well enough.
Personally I'm always wary of anything ignition related as I wouldn't want to have the security module fried/glitch/reset and have my ignition keys not working. But apart front the ominous note at the top, I can't see why it'd lock you out for just replacing an antenna coil. Maybe someone that's done this already can chime in.
McGyver'ing it with chewing gum might be the preferred choice.