Actually most cars nowadays, when talking about luxury, are very difficult to change out....lets remember this isnt a honda, also more and more cars are using computers for everthing in them.
That being said
Ok....for what you want to do, if your getting an aftermarket head unit, look up Darkwingfrog, MBai2, and a couple others....what they did was take the EXISTING radio molding, cut out the headunit, move a couple circuit boards for the DIC(display your talking about) then in the space that your headunit was in, slide any aftermarket into the locations....POOF...now you have kept the DIC, as well as adding aftermarket...Now depending on what aftermarket headunit you get, it will Have Ipod capabilities built in or you will have to add an adapter......
Dont forget that when you do this, you might as well add aftermarket speakers for the best possible sound
As you can see, its not a difficult project, but it will require some skill and patience.....or if you pay enough, your local guy can do it
