Ok, I got the info from my dealer. I have scanned docs, not sure how to share them here.
Bottom line is this:
If you're within your 5 year free service period, you have to pay for the modem (dealer quoted $318) and Ford picks up the labor.
If you're outside your 5 year period, you have to pay for everything.
And this is ONLY for Sync 3, 2016-2018 FFE.
2015 Magnetic FFE (aka Magneto) - Retired
2017 Kona Blue FFE (aka King Kona) - Current