I just finished installing an autodim mirror from an MZ4 (much nicer mirror) in my 135i. The best DIY can be found
here
A few notes.
1) Disconnect the negative battery terminal (and leave the trunk open)–this is in the pdf document but way at the front and you are playing with the car’s computer, you do not want to short anything.
2) The BMW retrofit harness has a solid brown ground lead going into the mirror side connector. When you open the stock mirror you will find that the solid brown would go to a brown/white wire location. Remove the solid brown wire from the retrofit harness, you do not use it.
3) No coding needed.