Control Arm installed upside down. How serious is it?

Either take it back to original place to get fixed or have a reputable shop or even a Hyundai dealer (best) to repair correctly. Have Hyundai work up a good complete estimate and bring your 1st original (complaint) service work order to place you bought car from and tell them "this is what I paid the H dealer to repair my car, and you need to reimburse me for this amount". This is very odd, and if indeed installed upside down or left side - right side, then there has to be a ton of strain somewhere in the suspension. Cant visualize your particular car but having over 20 yrs in certified auto repair..... sounds plain wrong. Even still the car is STILL making the SAME noise so return and let it be known that you are keeping an eye on things and as soon as you leave your going to a manufacturer dealer for inspection. Good Luck, will not comment on safety, I just cant.