How much will it cost to have a steering wheel installed with the radio controls?

I have an 03 Pontiac Grand Prix. It doesn't have the radio controls but I want to have it put on by someone who knows what they are doing.How much will it cost to have a steering wheel installed with the radio controls?
Only a person that works at Pontiac dealership can answer that question, that is because all parts need to came from Pontiac and is not a common installation. I guess you still have the factory radio. I think will be too expensive, if posible at all.