If your headlight bulb is burned out then you don't have to replace the entire headlight unit, rather you just have to change the headlight bulb itself. It's sort of difficult accessing the headlight bulb but here's the procedure on performing the job:
BULB TYPE: #H1-55W and #9005 replacement bulbs (low- and high-beam bulbs for 2002-2006 models)
HEADLIGHT : .
1) Take the keys out of the ignition and switch the headlights off. Then, open the hood using the primary and auxiliary release latches.
2) Use a socket wrench to remove the two 10mm bolts holding the coolant overflow bottle in place. Pull the bottle out of the engine compartment and set it on the ground (passenger's side bulb replacement only.)
3) Undo the bolt at the top of the air filter box, lift the top open and remove the filter from the engine compartment. Then, undo the fasteners holding the air dam in place and remove it from the filter box (driver's side bulb replacement only.)
4) Pull the entire air box out of the car to access the backside of the headlight assembly.
5) Turn the bulb socket counterclockwise to remove it from the assembly. Then, release the retaining spring, undo the electrical connector and carefully remove the old bulb from the socket.
6) Hold the new bulb by its plastic base and insert it into the socket. Reattach the electrical connector and replace the retaining spring.
7) Switch the headlights on to test the new bulb. If it works, reinstall the air box or coolant bottle and close the hood.