We purchased a 2007 530I a few months ago. This is our first Bimmer and we love it. During our research phase, we decided to place navigation at the bottom of the list and purchased a vehicle without it. I am now trying to research if it makes sense to upgrade the computer without the expense of going through the dealership. However, it's a very confusing world when it comes to understanding exactly what is required for this task. I found several computers on ebay, but I am not clear on whether or not is a simple exchange (plug and play). Maybe also the addition of a programming CD, or something much more complicated that will require the expertise of the dealership's service department. I would be very grateful to anyone that can provide comments on this subject.