Not as easy as you might think. You may want to go down to your LHS and take a look at an E-Maxx. If your LHS is anything like mine, they probably have one or two on display.
I am not saying it isn't doable, but it is not as easy as swapping out a couple of bits and going. This would be a swap the parts over a day and run the next day kind of transformation. In time, you might be able to knock that down to swapping in a few hours...but it is not a plug and play idea.
You could buy an E-Maxx chassis plate and build up the center section of the E-Maxx (all the parts that ride the chassis...batteries, tranny, motors, servos, etc.) and have that standing by. The E-Maxx and T-maxx share diffs, suspension, etc (basically the front and rear assemblies), so you would be able to just remove the front and rear of the truck and switch chassis pretty quickly. That would cost you some, but it is an option...and it would cut down on the change over time.