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Open the hood.

Loosen the plastic housing surrounding the headlights by pushing back on the black lever above the headlights.

Remove the plastic housing.

Disconnect the electrical connector by clicking the tabs together and pulling it out gently.

Remove the headlamp unit from the vehicle.

Remove the black plastic tab on the back of the headlamp unit by pulling on it.

Remove the side clips on the headlamp unit and remove the wire clip securing the headlight bulb into place.

Pull the burned out bulb from the headlamp unit. Use a paper towel to install the replacement bulb by pushing it into the headlamp unit.

Reattach the wire clips and the side clips.

Lock the black plastic tab onto the back of the headlamp unit.

Reconnect the electrical connector by plugging it into the headlamp unit.

Place the unit back into the vehicle and reattach the plastic housing. Close the vehicles hood.

Ensure the headlight switch inside the passenger cab is in the off position.

Open the 1998 Chevy Silverados tailgate.

Locate the two retaining screws on the taillight assembly (the screws were revealed after you lowered the tailgate) that has the faulty taillight bulb. Remove the two screws with the Phillips screwdriver.

Turn the assembly around and rest it on the bumper with the wire harness still connected to the underside of the headlight assembly.

Grasp the taillight socket and twist it counterclockwise 1/3 turn to remove the bulb and socket from the taillight assembly.

Pull the 3057 replacement bulb straight out of the socket and push the new replacement bulb into the socket. For the 1157 bulb, remove the old one by pushing down on the bulb slightly while twisting the bulb 1/4 turn counterclockwise, then pulling the bulb from the socket. Align the dual notches on the base of the replacement bulb to the grooves inside the socket. Push the bulb slightly downward while twisting it clockwise to lock the bulb in the socket.

Align the notches on the external section of the socket with the matching grooves in back of the taillight assembly.

Reinstall the taillight assembly and replace the retaining screws. Close the tailgate.

Park the Grand Prix on a flat surface, apply the parking brake and ensure both the engine and headlight switches are off.

Open the hood and approach the headlight assembly with the faulty headlight bulb.

Locate the headlight assembly retaining clip. Its behind the headlight assembly on top on the fender side. Lift the clip upward halfway to release the headlight assembly.

Pull the assembly out being careful not to scratch the paint on the fender or the lens of the assembly.

Reach behind the assembly and disconnect the wire connection and plug from the headlight bulb socket.

Turn the socket of the bulb counterclockwise 1/4-turn to remove the composite bulb from the assembly. Discard the bulb.

Install the replacement bulb into the assembly (handling the plastic socket part only -- oil in skin will damage the glass bulb of halogen bulbs because of the intense heat they burn at), but ensure the tabs of the socket end of the bulb are aligned with the notches in the assembly before turning it clockwise and locking the bulb into place.

Plug the wire connection back into the socket of the bulb before replacing the assembly back into place and pushing down on the retaining clip. Test the headlight bulb for operation before closing the hood.