Radioshack has the ability to send Ipod Nano's to the corporate repair center in Fort Worth TX, but does not employ technicians in their stores. For a repair a $20 non-refundable deposit is required.
Radio Shack has 6 repair facilities located around the USA. Each of them should be able to repair your Nano. You can simply take it to your local Radio Shack store and they will ship it into their assigned service facility for you - no shipping charges.
The $20.00 deposit only applies to repairs that are out of the warranty period. If you bought it at Radio Shack or have the original receipt showing that it is still within the Ipod warranty period, bring that with you so the repair will be covered under warranty.
The same guidelines apply to any product the Radio Shack has sold or is authorized to fix including, cameras, video, computers, telephones, and almost anything else electronic.