Please be sure it's unplugged first.
After all of the cover screws are out, the cover then should be slid slightly backward then up from the rear and it will slide off.
You may have to pat down on the sides to loosen it first. I use firm and simultaneous open-palmed slaps on both sides near the front, then pull it up and off.
When putting it back on, be careful that the inside front edges of the cover catch properly in the slots in the chassis.
Once the cover's off, there are Sharp edges and high voltages inside to be very concrened about.
If you or a friend decide to work on it, we have *critical* safety and disassembly info at our site, as well as other specific troubleshooting information and help.
In my professional opinion, people should not work on a microwave unless they are fully informed and aware of the deadly hazards and necessary precautions.
One can find such information and very specific in our safety and disassermbly text files at http://www.microwavedisplay.com
You can order parts for Sharp models from Tritronics at http://www.wehaveparts.com.
You can find wiring diagrams and parts lists and order parts for most other brands from the Pros here: http://tinyurl.com/gv383.
William Miller † MicrowaveDisplay.com, March 2007
