Hi mate have done this very same upgrade on mine, you have to change the whole nav unit to the newer BMW MK4 DVD based unit. The original range rover unit is the BMW MK3 unit which is very slow and has a rubbish menu system. The upgrade is really simple just unplug the old one and plug the new one in, I put the steps on how i did it on my website, www.myrangerover.co.uk then click on blog and it's on there.