how easy it is to find the speed sensor ford ka3 1999?

had my car diagnosed with speed sensor failure and i just refuse paying labour charges esp when the sensor is £105 on its own from ford so was wondering can anyone tell me where i can find or how to find the sensor i know what it looks like but unable to find is it a simple case of lifting the air filter housing out and it should be staring me in the face ???? many thanks :O)