Just adding to what Jerry said, yes it will work in an E-Maxx, but you will have to fabricate some sort of way to fit it in as it is not a direct replacement for the transmission. As far as the benefits over the stock transmission I would say that it is worth it, although I have not done the swap myself, the reduced weight and the addition of a differential in the center will really help on-power handling and acceleration.

If you are looking at putting one in, the easiest way to do it would probably be to buy Mike's Universal motor/diff mount and mount it to the chassis braces, kind of like this.