OK I'll Step Up!
The glass tray must be wrapped in several layers of *VERY* heavy bubble wrap, then braced in a sandwich of heavy cardboard or shipping box if not fit inside of same.
Racks if any can be wrapped in bubble wrap as above but would skip the boxing just make sure they are secured inside the main package. Or, if you can find a way to secure the rack inside the oven itself so it will not shift it *may* be done that way. What you don't want is for anything left inside the oven that can move about that will strike the glass door.
As for the oven itself splash out on a commercial shipping quality box that can support the heft of a Radarange. After taping the wrapped cord to the oven,I'd wrap the entire thing in bubble wrap as above taking extra care around the controls, then make a type of nest out of good styrofoam, tape and secure. You want the thing to be sung so it will not shift during shipping yet be protected against being thrown about and or otherwise manhandled via shipping. Think of the worse thing a shipper (UPS or USPS) can do including throwing the box down or against something and you get the idea.
Best of luck and congrats on your sale.