This was my first DIY project since getting my 2011 328iX. This DIY guide was of tremendous help, but there were some things that were not as clear from reading the instructions, and by writing this post, hopefully someone coming along could benefit from my experience.
My car came with plain mirror with no Homelink, autodim, or compass.
One thing that is incorrect in the DIY is that mirror is secured to the windshield using a spring loaded mount. It's not a screw, but a hexagonal nut that fits into a spring loaded clamp. Therefore, the mirror can be turned in either clockwise or counterclockwise direction 120 degrees to remove.
As you can see, my mirror did not have any existing wire harness.
I purchased my mirror on eBay for $95. Part number that was stamped on the back of the mirror was 015891 / 025891. It came with an existing wire harness 10 pin plug.
I followed the directions for removal of FZD. The assembly is held in place by metal spring clamp which is located in near the map reading lamp as indicated in the original post. By pushing in with a flat blade screwdriver or trim removal tool that I used, you are pushing in the metal spring clamp. FZD can be pulled straight down. It takes a little force and I was afraid that I might break the plastic, but it finally came down with no damage.
Once the FZD was removed, this is what I saw feeding down into the windshield.
I purchased the retrofit harness from ECS Tuning
https://www.ecstuning.com/ES161804/
Only thing out of the kit that I used was the wire harness consisting of 5 wires (Gry/Vi, Grn/Wh, Blk/Brw, Brw/Wh, and Brown) and Black 10 pin socket housing. First thing to do is to remove the black rubber grommet. It's held down by cloth tape and can be coaxed loose with little back and forth motion. Once you are down to 5 wire harness held together with some cloth tape, you can feed the wires through the existing rubber grommet at the top of the windshield using the straw trick shown on the OP.
Once the wires are through, just attach the 10 pin black socket from the retrofit harness kit to the wire as follows:
A1 Gray/Violet wire to Pin 1
A2 Green/White wire to Pin 3
A3 Black/Brown wire to Pin 4
A4 Brown/White wire to Pin 5
A5 Brown wire to Pin 10
The other end of the wires also have pins except for the Brown wire which is left bare.
These wires are connected to existing socket that goes to the FZD. In my case where I did not have any existing connections in my original mirror, I followed the following instructions.
Gray/Violet wire to Pin 14
Green/White wire to Pin 20
Black/Brown wire to Pin 15
Brown/White wire to Pin 16
Brown wire was tapped to much larger Brown wire going to adjacent connector X14287.
At this point, I connected the new mirror to the newly wired harness and cross my fingers as I switched on the ignition. Light to the compass on the mirror came on and I knew I was good to go. Reassembly was much easier. FZD just snaps back into the overhead slot. Mirror twists on the windshield mount and cover behind the mirror just snaps together.
I followed the directions to calibrate my compass
and programmed my Homelink. Everything works and I am a happy camper.