sound like a huge big job "unplug" everything (entire interior) before you can "plug and play"...
if you have a double din touch screen just connect to the sat nav housing unit (off course you havta mod the sat nav unit first) as a top second screen coz get a lot complaint the stereo screen sat too low
read few diy guys try to install a full original sat nav system from another IS200 but ended selling the lot in the end.
as Ian say "you will need all dash loom from same model year as yours" making sure it does works or you gonna sit there scratching your head like a cute pug
if you know what you doing you could give it a try
good luck :zee: