I take it you are on about a Transit RWD? The service light-ignition on and hold the throttle and brake pedals down for about 10 - 20 secs,it should start to flash,ignition off and it should be reset. I have no doubt the Ford workshop had good reasons to condemn your module but the glow plug light indicates a fault and a good code reader would be the way to go to determine what fault codes are stored,you can guess if you want but can guarantee it will be an expensive business changing parts which don`t warrant it.have had heater fans burnt out on these and may be worth a look at also seeing it happened in your cab.Good luck.
cdc, February 2014