First thing to check is the solenoid on the passenger side of the shifter. There is a plastic 'tab' that sits in a small slot on the solenoid. When the key is in and the brake is engaged the solenoid 'shuts off' and the shifter can be moved. That tab may have come out sometime during your bulb replacement...explaining why the shifter would not go all the way into park.
Also, the metal shaft that the shifter attaches to has a plastic rod in the center of it. The plastic rod is what moves up and down when you push in the button at the top of the selector.
