I'm suggesting you only have one problem. The radio code is input by the owner, just follow your manuals instructions. The issue with coolant, unless you are seeing it on the floor, there is no problem. Especially true if it has been going on for some time and your temp guage shows normal. The coolant reservour will look practically empty in very hot environments. Is your "low coolant" lamp on? probably not. You do indeed have a problem with the car however shutting down. You have to figure out if it is fuel or ignition related? What you describe is a popular failure with the fuel sender. If the sender stops working, if only for a second, the engine dies.