Car horn does not work, and the airbag light is indicated on the dashboard.

Hello, Yes a Cadillac dealer can repair this issue, but so can many more cost effective facilities. The likely cause is called the SIR coil, or clock-spring. It allows the steering wheel to turn while still maintaining an electrical connection to the steering wheel buttons, horn and airbag. Diagnosis can be performed by any trained technician, but for peace of mind, use an ASE certified technician, or, as you mentioned, the dealer (is cost is not the concern). Here is a list of certified trusted facilities in your area, that have the proper training to complete this repair: http://repairpal.com/cadillac-within-10-miles-of-portal-georgia-30450