I am buying a 2006 navigator ultimate 2wd with 49k miles tomorrow hopefully. It has everything I want except the radio is not the navigation unit. I looked at another 06 and it did have navigation. Is it possible to buy a new or used nav unit for the 06 model and install it into mine that does not have the nav unit? I read I might need a gps antenna but do not know where to get one of those. If it is possible as they are the same year what are the steps and what do I need to buy?

At the very least, you need the disc reader that is in the center console. Just installing that could be a serious undertaking considering what may be involved in getting to it.