Welcome..
I know only enough to be dangerous but I thought I would get the ball rolling and those in the know will chime in. I believe you will have to replace your radio module that is in the trunk with a newer satellite ready module (I think produced after 10/2003 but not sure). Otherwise there are some other alternatives but I don't think they allow you to view the title and artist in your dash.

Edit: I just looked on the x5world front page under stereo I think articles 27-35 deal with this subject.