Dear Hoot,
You can get the Mamba USB cable from the IRC Racing web store
www.internet-rc.com and I know that iti is in stock.
Shim kits are available for about $2-$3 from hobby shops. I heard that shim kits for the Kyosho mini and the Losi will work on our diff.
Without visually seeing the diff and actually playing with it, I really can't tell you if it is the diff and if it is salvagable. But, clicking out of the diff box is not a good sign. You may have to replace the diff.