I have just seen the message on my dashboard stating that I need to replace the Key Fob Battery as it's getting low. I have the regular remote central locking Key Fob (The regular, Non-Keyless Entry variety). Do I have to take the key in to the dealer to get the battery replaced or is it something I can do at home. If I were to replace the battery will it screw up the key coding between the the key & car? If replacing the battery myself does not affect the key coding to the car, what battery do I need to purchase?