Hi there!
I found a couple tutorials for similar microwaves, hopefully they at least give you an idea of how to start!
Here's a [https://www.youtube.com/watch?v=NJm3GOMUszg|youtube video guide|new_window=true] for handle replacement, and a [http://www.appliance-repair-it.com/GE-spacesaver-microwave.html|blog guide|new_window=true] showing handle replacement on a standard spacesaver. (Also here's the [http://www.homedepot.com/catalog/pdfImages/3e/3e9488f5-852d-4dcd-84c2-1fa4c6de6757.pdf|user manual|new_window=true] that has some support phone numbers). Best of luck!