After getting my '06 back from the shop (the result of a pretty good accident), my ext. temp display in the gauge cluster is blank when I turn the car on, then it reads "---?F"

I'm guessing the sensor is disconnected, and I'd rather plug it back in myself if it's not too hard to do. Does anyone know where the thermometer is that is reads from, so I can check that, and where else I could check to get this guy working again?