I just picked up a 95 540 M-Sport, which is the model pictured in the photo. I went out looked underneath for you and I can't say for sure if the lower lip is a separate piece. Although there is an external seam visible, the lower lip and bumper valence look as 1 piece from the backside. Maybe if I had a lift and better light I could say for sure.

This illustration in the ETK seems to support what the dealer is saying (that the lip is part of teh bumper assy)

http://www.realoem.com/bmw/showparts...39&hg=51&fg=15

Let me know if you want to try and eyeball any other details.