I took my car for service and it came back with several lights on the dash and no bass in my audio at all... Any recommendations?

I would definitely take it back to them

whats the average cost for a diagnostic.. And whatcan i expected to pay hourly for labor?

You didn't notice the service lights when you left the dealership? Either way I would call immediately and ask one of the service reps about returning the car to be checked out. They have always been great about resolving any issues I have had in the past.