Ecu change, vin change

I am having issues with my 04 cts. Problem is a no start and key will not turn back to lock and no gauges but power is on. If I leave key in start position, jump the starter relay, she starts and runs fine, but I have to do that, then shut off, remove key, restart as normal, all good. It will restart every time as long as you do not let it sit too long. I assume ecu is bad. I have a replacement. So do I marry my credits to original ecu and Vin, then swop out ecu and change that to car vin? Or do I need credits for both ecu's. Thanks in advance.

Program it with a GM Tool to the vehicle. Then license the computer.

You will spend $200+ in credits if you have to license both computers and it may still not work if something doesn't go right when trying to do that flash. It could brick the computer.

GM Tool?

Yeah, like a Tech 2 or GM MDI scan tool.

If you know someone with a scan tool like that and a subscription to the website you would do it that way or bring the computer/car to a dealership to have it flashed. This is a best way to go about programming a new/replacement computer.

OK thanks

Does both of the software numbers need to match on each of the ecu. Hardware and software OS. on each one, original and replacement. Hardware OS is same number but software OS Is not?

Could someone explain the first paragraph in this. Correct me if I'm wrong. Replacement ECU installed, tune open for original ecu? https://www.hptuners.com/help/vcm_ed...change_vin.htm