Honestly, I would get the new one and be done with it.
If it doesn't work after that, then I would recommend small claims court. Get the money back.
People seem to put up with the whole replacing things, until something sticks approach.
If they fix it and it doesn't work, they need to keep going at their own expense and remove the crap the put in after they are done or leave it that way. Either way, you only need to pay for what is actually non functional.
My 2c.
And forever drive a car that drives like a piece of ****.
As someone who has "tried" this approach recommended but some genius when I had a stuffed ECU. When you go aftermarket with your ECU, your car becomes a complete piece of sh#t. Drives like sh#t, no security features, so many things I won't even bother to mention. Generally your car is just cheap with an after market ECU.
If you drive a Citi Golf or car made before 1990, then sure. Anything more advanced than that and after market is a down grade due to the general low quality of after market units. Not to mention all the "tuning" needed to get it to "work".