I have that shredder too, It's a good shredder.
Mine quit going forward as well. I rewired the switch and it goes forward, but not reverse. Which makes it a saftey issue and I wouldn't recommend you do this, unless you are comfortable playing with the wires.
My thoughts are that it is the switch which needs replacing.
I found this number while searching this site. Maybe it will help you get some answers or parts or both.
Royal Consumer Parts
1-800-222-2310
option 2
Royal 3, January 2009