Off-course Daewoo has automatic fan system controlled by the ECM (computer). There is an option of installing a thermostat switch (not the thermostat valve) in the radiator, but not really required if everything else is fine (sensors, ECM, wiring).
Regarding thermostat valve, it should be kept installed because it helps the engine attain and maintain optimum temperature. Mechanics usually remove the valve, which can cause permanent damage to the engine components in the long run!