The part was on sale for $140 last night. Keep searching for it.
MSRP $199.
Labor is 1.5 hrs for US (suggested). That means $200 range.
So, dealers are likely to quote you around $400.
Negotiate the cost with that in mind.
There is a guy on youtube who showed the entire process very clearly.
Search for "Mazda android auto install", and you will see it. His name is Greg. Young Asian dude.
If you dare to DIY. $150 total is possible.
Firmware v70 is required.
part-I:
https://www.youtube.com/watch?v=lOETm9Az2yw
part-II:
https://www.youtube.com/watch?v=Op6A5_e3ncU
Sounds like overall the upgrade isn't worth the expense.
Honestly, I don't know why people complain about Mazda Connect concerning most of the everyday things you really need. I'm sure there's some people who do heavy phone related things that would really appreciate AA/AC. Particularly with voice command accuracy. My biggest gripe with OEM navigation is the inputting part of the task. With Google maps you just speak the address and it almost never fails. Not the case with Mazda's nav or many other OEM's. If I want the ease of Google maps, ultimately I can just mount my phone.
$400? I wouldn't do it after using both setups. I just get it my car and listen to XM. Sometimes I'll stream off my Google Play library in which AA doesn't really add any value. It's still on the display through Mazda Connect.