Which tank?

Are you talking about the smoker switch on the board? Simple, turn it on and cut it below the height of the heatsink. Then rig a remote on/off switch on the negative side of the smoker wire.

Some guys swear buy big giant 40mm PC fans, I've had great success with Novak 25x25x10mm fans from Tower hobbies. They're pricey and pull a lot of air and haven't failed me yet.

Binding? Have you taken the gearbox apart? You might want to separate the halves and spin each gear by hand to see if there is a problem with any of the bushings/bearings they ride in. Remove the pin ejector marks on the inside of the gears as they can rub and break them them in again, for hours if you have too, you want them to freely spin even with the motor attached when you're done for peak efficiency.

Look up my builds for pictures and wiring diagrams with the fan, there are lots of ways to do it if you don't like mine.