You'll need to take the oven/microwave out. On the top of the oven/microwave there is a small access panel (2" by 2") at the front.
You'll need a special screwdriver to take the two screws out (I used a pair of pliers - they worked).
Inside the housing is a 40W small anderson round bulb.
Just replace that ... and you'll have light.
JB, October 2011