How do you replace the headlight bulb located on a Oldsmobile Delta 88?

Lilely

For non-sealedbeam headlights - look under the hood behind the "bulb" and you should see a wire connector and then a plastic lock ring in front of that about the size round as a coffee cup. Twist the ring counterclockwise and remove the bulb. Lift the retaining clip on the wire connector just enough to pull the connector from the bulb socket. If you have dual headlights you can swap the two bulbs on one side and be back in business because the bulb has two filaments and each light uses a different one. On the passenger side I had to remove the battery to get to the bulbs.