gm makes and has calibrations for "upgrades" you just have to message with them and tell them what you are trying to do, you need a paid vin of course and the part number of the module being added.
obviously they made these with different trim levels, so all they have to do is edit the calibration file they provide (upon request) to work with your vin.
all they have to do is look up the part number being added, find the associated calibration file. attach your vin to that file and save it.
then they just give you the calibration file number that you enter into sps to program your vehicle
that's my basic assumption of how that works, I do not know if they charge "extra" for that or not.
I know it can be done because there are gm service bulletins on "how to" that have been provided to dealers when dealing with upgrades
I didn't know this until after I had tried the radio upgrade and started looking into why it didn't work like I expected it to and that point I just said f-it I already was past doing it and made something else work.
I had no idea they would do that for you. that sounds like what it would take.
almost sounds to good to be true. gm isn't usually very helpful. what phone number would you call for something like that?