hi, I have a E39 and have the standard stereo with the disc changer in the boot. I would like to fit the 16.3 sat nav into the dash. Somebody told me it was as easy as taking the stereo out then replacing it with the screen. I have now been told this is not the case and is very involved. I have bought the screen and a module but do not know what else i need to carry out this upgrade. Anyone on here done this before?