1998 Camshaft Positioning Sensor

i recently had my car inspected and it failed because they said i had to get this sensor replaced. i was told today by a mechanic that he believes if this did need to be replaced the car wouldn't be able to run. is this correct? can anyone help me before i go pay to have it replaced if its unnecessary.

I would think he would be right, although I couldn't tell you where/how to replace it.