Well, the step by step directions are in the link I posted and followed those... but I guess my version is...
1. buy a home link mirror from a salvage gla or cla on eBay and harness 156-540-56-05 from Pelican Parts
2. Remove the rain sensor cover and SOS buttons. Be careful with the SOS buttons as they have a clip that has to be compressed first and then pushed down otherwise it will break.
3. Drop the N70 overhead unit by pushing up between the back of it and the headliner. It’s spring action that needs to be pushed forward to drop it down and you need more force than you’d think. The hack here is to use a plastic spatula that is wide enough to make contact with the whole spring piece.
4. remove the old mirror with a wrench (there’s two grooves on the back of it to hold on to) and unplug the single wire harness.
5. Insert the blue end of the new harness into the blue end coming off the homelink mirror and then remove the three wires from the white end. You need a couple paper clips as the plug has a two step process to get the wires out (see below pic). It doesn’t matter if you mangle the white plug getting the wire off as it’s not used, just make sure you don’t damage the wires if you have trouble and start hacking.
6. Attach the home link mirror to your car and insert the white plug that was already there from the original.
7. On the passenger side of the N70 overhead unit when it’s dropped down is a white plug (pretty sure it’s the middle one). Insert the three wires from the new harness into their corresponding spots in the white plug just mentioned above in this step. This whole entire process really needs to have the credit given to the guy who originally figured out where to put the three wires. His original picture is below.
8. Reassemble everything and you’re done. No programming or anything needed. To check if it works.. take your finger and cover the sensor on the backside of the mirror and then shine a light (like your phone) at the sensor on the front of the mirror and if it tints blue you’re all good. The test won’t work unless you cover the front sensor.
Good luck. I could provide better details on any of the steps if anyone needs it.