I would start with the basics, we need to know if even a simple command works before trying other stuff. I would try a few commands. Something like this to zoom in and then out.
void setup() {
Serial.begin(4800);
}
void loop() {
Serial.print (":WFCBB99"); // zoom in
delay(5000);
Serial.print (":WFCBBFE"); // stop
Serial.print (":WFCBB9B"); // zoom out
delay(5000);
Serial.print (":WFCBBFE"); // stop
delay(1000);
}
Then if that works try some other stuff. If not (I may have been wrong in my interpretation of the specs) there's no point continuing until you figure out why.
NOTE: You are using Serial, this is connected to the USB chip which often causes problems. I'd swap to SoftwareSerial and use two other pins.
Rob