Does anyone know how to update Ford DVD Navigation System in a 2004 ST220 Estate? i currently have DVDR Ford Part No.3S7T 10E898 AB DENSO Part No.464210-5260. Do i need a new disc or do i insert update disc then insert above disc after? can i download update or is it best to buy new disc? ive been offererd a 2010 copy from a 2005 Disco3 but not sure what may happen?