Changing the light bulb in a microwave oven can be done by anyone with little or no skills. Manufacturers do not include the directions for the consumer to do this task since they consider it as an appliance repairman's job. Save yourself some money and do this yourself; you will be gaining experience for future light bulb replacements as well.
Unplug the microwave oven from the outlet. Wait 20 minutes for the capacitor that is inside the microwave to discharge.
Unscrew all the screws around the casing by turning them counterclockwise.
Remove the cover by lifting off.
Locate the light bulb in the microwave. This will be located on either the right or left side.
Unscrew the light bulb by unscrewing counterclockwise. Some light bulbs are held into the socket by two notches; for these you will need to gently push on the bulb and turn counterclockwise to unsecure the bulb, then pull out of the socket.
Place your new bulb in the empty socket and secure by turning clockwise until tight, or if the bulb is one with notches on both sides, then guide the notches into the slot on the socket, push gently and turn clockwise until clicked into position.
Replace the cover and screw back on. You are now done and may plug back in the microwave.