Will I retain full functionality of my vehicle after the upgrade?

In almost all cases, yes! Your back up camera, steering wheel controls, climate controls, etc. should all still work after the upgrade. 

There are some issues with on some CGEA 1.2 vehicles with Sync 3 and software version 3.4 (older Explorers for example) where the dual climate button may be flip flopped; it will say it's enabled on the climate panel but it will be off on the display. The fix for this would be to run software 3.3 instead.

If you have a 2013 or 2014 F-150 Raptor, there will be a couple more steps that you would need to do to enable your off road front camera.