Transmission Speed Sensor

Does anyone know where this sensor is located? Is it easy to replace? The shop said once I replace it my check engine light should turn off. Does this sound right?

2000 Jetta 2.0 GLS

Cheers

Manual or automatic?

Automatic

It's on the top rear of the transmission, sort of behind the engine. I think there may be another closer to the battery. If I recall correctly the rearward one is for the spedometer.