My 320d did not have ambient lighting but my 330d does it even has the lights on the outside handel and when you open the door it has the logo projectors in the bottom of the doors. So in short the door pannel trimmings are different and also you will require wiing to all doors. Also you can adjust the ambient bightness and color on the idrive. Not sure but I hink that retrofit will cost you a pritty penny.
Only thing I changed on ambient light is that I coded the brigtness adjustment is seperate from the dash brightness. And fitted some plastic strips in the door so that it shows a slight line in the dark like the 5 series