Do it the right way, and get the kit from Mazda.
Buy this, it has all the parts you need:
https://www.prioritymazdaparts.com/oem-parts/mazda-smartphone-screen-mirroring-kit-00008fz34
Carefully ready through the first three posts on this forum. It has all the information you need for the firmware upgrade:
https://mazda3revolution.com/forums...ay-android-auto-all-here-now.html#post2405671
Watch these videos, they will guide you through the install process:
https://youtu.be/GYEaddWnbiQ
https://youtu.be/8choSrR3f-M
Other than that, the only other tools you need is a philips head, 10mm socket, and plastic stick tool (I used a butter knife in its place).
You don't need to be tech-savvy to do this upgrade, but you do need to be good at following instructions, especially during the firmware upgrade process.