Use CarPlay maps instead. Apple CarPlay nav info is updated all the time, and is the simplest to use. Don't ever pay outrageous prices for GM nav updates that are at least two or three years old when they release them. Just my 2cents.
IF YOU WANT TO BUY A 84157655. Get it touch I have one.Just purchased our first ever Buick this week (Envision Premium 11).
Very happy with the purchase decision overall, but have found one irritation.
Have an issue with the navigation information. Roads and speed limit info is at least 2 years out of date. While dealer and GM customer service tell me I have the most recent map version for my vehicle, neither can tell me the version number. That was an hour or so of frustration and call transfers to multiple GM staff.
Mine has software version 84009390, which is also in many other 2016 GM vehicles. On the GMnavdisc order site this map version has been updated by various versions (84157655 and 84201676) for 2017/2018.
Not happy that a brand new 2017 vehicle does not have the most up to date map software. Hoping that GM will do the right thing and supply 2017 map software for a 2017 vehicle.
Did find out that my 2017 was actually built in August 2016.