How Much Does It Cost To Fix A Gas Gauge?

I recently took my car to the shop to be repaired.  It was put on the Performed Computer Diagnositc and found Code Po341, Cam Sensor needed to be replaced.  It was replaced and when I went to pick up my car the gas gauge was broken.  It seems to me that it went clock wise all the way around to E and stays there.  My gas gauge was working perfectly when I took my car in for repairs.  What could have happened for this to happen?

Thank you