I belive that Chevrolet with the tilt colum has a wire connector (as in coat hanger)between the tumbler and the actual electrical switch that sits further down the steering colum.
The electrical element is a sliding switch and is moved via THE wire that sits on a small ear, that ear has a tendency to brake, sometimes on and you can not turn the engine off you are dead in the parking lot.
To replace the switch, the steering wheel needs to come off, if yours has an airbag you need to let the vehicle sit with the battery diconected for minimun 24 hours so that the capacitors in the air bag cirquitry discharhe, otherwise you may have a nassty deployment.
You also need to be a contortionist to extricate the old unit and install the new one since it has to pass trough a very small opening, lots of patience and luck.
The actual mechanism behind the tumbler is metal but I have seen them brake, pot metal, metal fatige.
You need a special tool to remove the pivot mechanism in order to get to the rest of the colum, you might need to leave this to a proffecional.
Hope it helps a little
navegator