I was able to retrofit my CIC for around $300, $70 for the head unit and $70 for the screen (got very lucky) and $150 for brand new cables and trim. However my CIC wasn't the latest version so I went out of my way and spent $800 for an ICOM cable and updated it myself.
This is the guide I followed, the only hard part was gathering the files and setting up the environment but in the end it works perfectly. The easiest part was getting 2021 Maps on it as well.
https://www.e90post.com/forums/showthread.php?t=1649066