At our site, we have a service manual for a different Sharp model that should be similar enough to help you.
It's at http://www.microwavedisplay.com/r1380_r1381_sm.pdf
While the part numbers are different, etc., it should provide you enough safety, disassembly, and other help that you can get the job done.
If your local home center does not have the bulb, you can order parts for Sharp models from Tritronics at http://www.wehaveparts.com.
You must unplug the microwave when you remove or install bulbs, especially the ones that illuminate the stove top, or you can easily damage the control unit / circuit board. We get a lot of these in for service!
William Miller † MicrowaveDisplay.com, March 2007
