There is some kind of plunger that holds a shaft in the detent - im not sure if the plunger is a switch for the backup sound or what??
I think you might be looking at the ignition switch on the column. Does it have a thin rod going into it? Turn the key and see if it moves.
The shift lever attaches to a tube which runs inside the column. At the bottom of the column is an arm with a relay rod to the trans. At the trans end of the rod is a slide adustment. This attaches to a flat arm bolted to the trans. I would check the trans end first, tearing the column apart is a lot harder and it's usually a linkage problem.