till the lights go off on the MKIII. Slide it out and pull the antenna plug straight off, press down the small detents on the 2 main plugs and pull back the latches to unplug them. Connect the 3 plugs to the MKIV and slide it in place. Enjoy. Up date the OS on it if it does not say 4-1/00 in the upper right corner when you hit settings. Even better find someone with Navcoder to delete the accept screen and put in your VIN (Not all necessary but nice to do). I have forgotten which menu you go to to enable perspective view. You should go to xoutpost or bimm erboard to get more nav info.
What are you going to do with your MKIII? What is the P/N of it? Let me know.