Personally I would't change the plastic spur gear with a metal one. If something has to give, would you rather it be the spur gear or a tranny gear? That's why they make the spur gear plastic!

I've had my truck for a couple of months now. Love it. I've beat the crap out of it and the only things I've had to replace is the spur gear and brake pads. The brake pads were my fault as I forgot to adjust them after I added a reverse module and a new servo.