I'll leave the detailing tips to others, suffice to say it's real wormhole if you get serious about it!
Regarding the Android Auto enablement. I did it on my 2015 car back in October when I bought it. The car had the App Connect function, but if I pressed it it displayed a message telling me to throw some money at a dealer if I wanted it to work.
After much Googling, all I had to do was download some free firmware from the 'net and upload to the car via the SD slot. I didn't pay for anything or need any diagnostic tools and it has worked perfectly since. I was super nervous doing it in case I bricked the head unit or something, but it was straightforward in the end. I posted the link to the guide I used here:
https://www.golfgtiforum.co.uk/index.php?topic=290914.0