First thing I would do is check that the thermistor is working, maybehold a soldering iron close, or hairdryer, and see if the temp goes up.
Then a multimeter across the heater pins on the board, to see if it's turning on (should see 12v). Then maybe multimeter to measure the resistance of the heater, to make sure it has the right resistance (some are about 4ohm), as long as it's not a short circuit or open circuit you should be fine.
