Well, I doubt the smoke unit needs to be replaced. First step is to determine what has failed. For PS/2 smoke units, unless you happen to have a runaway that burns up the PCB, the wick, motor, and resistors are the things that typically get replaced.
A sudden failure leads me to the smoke unit not getting heater power or motor voltage. When you run, can you hear the motor pulsing if you enable smoke? If not, do you smell the odor of hot fluid when you sniff the stack?
Did you do a feature reset, delete it from the remote and add it back? Did you closely inspect the tether?