I didn't see a DIY on this yet but there were some discussions about it on another forum so I took some pictures as I was wiring my own V1. Steps are as follows:
Tools:
1) Radar detector
2) Mirror tap:
https://www.amazon.com/Radar-Mount-M...=v1+mirror+tap
3) flathead screwdriver
1) Pop open the front black panel of the rearview mirror
2) You will see the red harness which i believe is the harness for the rain sensor. Using the mirror tap from Amazon, tap the positive and negative terminals into the far left and far right pins of the harness
3) test that the radar turns on and off and you're done.