On Board Navigation

I'm looking for info about the navigation system. I just took delivery of a 2003 530i w/o the navigation system. I asked 2 dealers (service) about the installation and got 2 answers. One said yes they can do it and the other said no, it can't be done. I would guess that all the harnesses are put in place at the assembly point and depending upon the ordered options the terminal ends are connected according to options.
Any one can answer this?
Thanks
Jde