Radio/tape Cd Player problems of the 2008 Chevrolet Aveo

When using the cigarette lighter the fuse was blown on the radio. Now the delearship is asking for $120. 00 just to give us the code.

I was driving on high way radio shut off and dash lights flickered. Then it was fine then I go and turn car on dashlights not on and car wont come out of park. Also headlights keep blowing out.

Air bag light came on and stayed on. , dashboard clock and cd radio also went out. The cevrolet servicing dealer suggested that the service codes reflected a short in wiring and the dashboard has to be removed to check the wire harness for the short. They wanted to charge me $315 , manager continued to state also the sensor modual for the airbag may be defective. Why do they charge for diagnosis when their diagnosis measures cannot find the problem and want to charge another $315 for furthur diagnosis?I with th ive cheched with other Aveo owners and some have the same exact problem. I do believe there is a fault with this car. I do not know if the airbags will deploy if their is an accident with this car.