Hobbit50

Hi everyone - can you help - I have just purchased a 2003 Rx300 series 2 which still has the original 2002 sat nav disc installed - which means no postcode search. Does anyone know whether the later map updates come with a postcode search facility or alternatively whether it is possible to replace the Sat Nav computer with the later Gen 5 variant from an RX400 which does? Any help or thoughts gratefully received.