Even if the rx18 board worked, which I doubt, you would be way underpowered. Remember the Stuart is a 12 volt system. Go with a Sabertooth 12rc it will handle the tank with ease.

I've done my Stuart, 3 others and a pair of 1/9th 21st Century Abrams with em, and they do just fine.
Since I already had a DX6i tx, I used an $8.00 Hobby King 6 channel rx, in mine. For the others a Turnigy 9 and 8 channel rx.

Only modding you would have to do is use a servo operated DPDT switch to operate the turret. I ditched the missile launcher and installed an Airsoft cannon, used a servo to fire it, and a second one to operate gun elevation.

And a sound board is nothing to add.

Here's some of the ones I've done.