This is one of the first mods I did to my Z3 during March 2000. It was a perfect wintertime project, it was inexpensive and could be done quickly in my unheated garage.
1 I followed the instructions on MZ3.NET and ordered BMW parts:
63-13-2-493-613 left clear front marker light
63-13-2-493-614 right clear front marker light
from Circle BMW. I think I paid around $15 each, list is approx. $18. Push the side marker towards the front of the car and lift the rear of the marker out first.
2 After removing the marker assembly, simply disconnect the wire to the lamp. Here is one of the original orange markers.
3 I then used a cotton detailing towel and some Griot's Speed Shine to clean the accumulated crud around the mounting hole. Installing the new markers is as simple as reversing the previous steps. Ten minutes later and you are done!