My car was built before September of 2000 so it did not come pre-wired for the Voice Recognition System. Fortunately, BMW did make an adapter harness so the install can be done. This model year (as well as 99 and half of 98 I believe) does not require any replacement of steering wheel buttons as long as the car is wired for a phone.

Here's the required parts:

84-11-0-027-947 -- E38 SES Kit
84-11-0-029-707 -- SES Jumper Kit
Double Sided Tape

Step 1 - Remove the two screws to the right of the CD player and the Nav CD Drive. They are a bit of a challenge to get out. As I unscrewed them I slipped a piece of cardboard behind the screwhead to keep tension on the nut.

Step 2 - Remove the Nav CD. The "tool" is made from a coat hanger

After you get the Nav CD drive out and disconnect the wire, you can carefully remove the grey shroud that covers all of the electronics.

Step 3 - There is a 12 pin connector by the left tailight assembly. Unplug the two pieces and connect the corresponding connectors from the harness (Sorry about the blurry image).

Step 4 - Fish the connector for the telephone mic out from behind the bracket shown in the photo, disconnect the two pieces and connect the corresponding connectors from the harness.

Step 5 - Connect the blue connector on the harness to the SES unit and apply some double sided tape. (There is a bracket you can buy, but I elected to just use the tape.)

Step 6 - Mount the SES Unit on the bracket that holds the CD Player.

You're done! Reinstall grey shroud and Nav CD. To activate/test, turn the ignition to position 2 and press the phone switch. You will get a new tone and "Voice Activation" will show on the LCD in front of the steering whell.