Couldn't be easier, this procedure was performed on an 01 530 with Non-DSP. The procedure should be the same for all E39's.

1) Locate the volume knob. It simply pull right off.
http://i47.photobucket.com/albums/f164/gray1g/step1.jpg

2) Once the volume knob is off locate the allen head screw under the stem that holds the knob on.
http://i47.photobucket.com/albums/f164/gray1g/Step2.jpg

3) Using IIRC is a 6mm allen key insert into the screw hole(Oh baby) and give a 1/4 turn or so.
http://i47.photobucket.com/albums/f164/gray1g/Step3.jpg

4)While the allen key is inserted, pull out the head unit. If you want to totally remove the unit detach the wiring on the right hand side. If you need to find the S/N # it's located on the back. Thanks to another member I found that if the key is in the 2nd on position with the radio on, you can hold the m button in for a few seconds and it will display the S/N # along w/ a ton of other info.
http://i47.photobucket.com/albums/f164/gray1g/Step4.jpg

cool i was tring to figure this out i cant believe how easily it is thanks man

Thanks for the pics. I noticed you have the same crack on the CD wood flap as I do. It's a lousy design to put a rigid (lacquered) surface on a part that is flexed every time it is used.

To remove the wiring harnass from the MID, there is a latch mechanism on the connector that has to be unhinged by rotating it towards the front of the MID unit. It took me a few minutes to figure out how to disconnect the harnass.

To remove the CD player, there are two set screws at the bottom of the unit that holds it in place. There are 4 connectors on the CD player.