I don't want to jade you too much on this - so I think as a primary objective you should follow normal TMC mantra and try to get this resolved to your satisfaction with your service center. Basically hope for the best. As brkaus noted, the estimated fee is not billed to the owner for warranty work.
But I would be remiss if I just ignored the experience we received. So, If you want to mentally prepare yourself, there is possible outcome where no root cause is identified. In my experience the service team simply reset the codes and asked me to prove I ever had any error codes. They were visibly annoyed I had bothered to take pictures with my phone and had posted them online. Anyway, they asked me to keep driving it because they felt these types of errors happen all the time.
If you personally are not ok with that type of resolution path, I'm afraid you purchased the wrong vehicle from the wrong company. Basically you're SOL.
The only reason our household received a buyback was because we had a completely other issue that was unrepairable within 30 calendar days.