Body control module change?

Hi, thanks for reviewing my BCM problem. First a little history. I had issues with turn signals and hazards none work at all. I diagnosed it as well as I could then learned it could be the BCM. Had garage verify and they found same p/n 15886074 (used) and installed after flashing the donor BCM. After that I went to pick up the truck and noticed dash displaying check engine and airbag lights on. Also indicated change oil. Mileage increased from 118,000 to 195,000 and radio (GM Delphi) locked on AM/FM bands and XM radio also locked. The garage cleared the dash trouble lights and engine oil and sent truck out for gm dealer to unlock which they did (AM/FM bands only go figure).
Doing some reading online I leaned the XM radio is tied to the vin# as an antitheft mechanism. The radio as well. The odometer updated from the BCM on mileage and VIN#. So, I'm thinking the garage did not properly flash the donor with the appropriate data. If they did then the mileage would have been fine and the radio working as well.
I would like to try swapping the BCM from the current installed (my truck does run by the way) with the original to see if XM radio works again. If I do this, would I have to perform a pass key procedure on the vehicle after I put in the original BCM again for testing purposes. It is a pk+3 system. I have located a vendor that will reprogram the donor BCM with the appropriate vin# and mile (and other data I assume) that is on the original, so I can plug and play. What are your thoughts on this mess? Can I swap current with original to test radio functions and then send out odometer and both BCM’s for flashing again. Will keypass procedure be required during BCM swap and final installation?
Thanks very much for your input. I'm not a mechanic, just a guy trying to get the XM radio and mileage back to what it is supposed to be. I have receipt of BCM change for proof of mileage at time of repair which I need if I want to validate mileage. Such a headache.