Remove the door from your GE Advantium microwave by lifting the door up and prying the hinges on the door off the oven body. Use a standard screwdriver to pry off the hinges.
Lay the door on a bath towel covering a tabletop to ensure you don't scratch the table or the door.
Pry back the edges of the door to release the plastic fascia. The fascia has little fingers that will probably break off, but be careful to not damage the trim.
Unfasten the top door handle screw using a Phillips screwdriver.
Unscrew the six screws that fasten the door to the outer trim. Gently pry back the plastic trim to remove the core from the trim. Remove the lower door handle screw and remove the handle.
Install the new door handle by reversing the steps you used to remove the old one. Use a pair of needle-nose pliers when replacing the screws that hold in the core. The space is too small for your fingers to fit, and the pliers will help get the screws started so you can finish tightening them with the screwdriver.