So I actually bought an extended warranty through EasyCare which was given to me at a very discounted rate because of the entire situation. I have used EasyCare in the past and they were easy to work with.Might consider asking them for a GM Protection Plan to 8 years and 120K miles? Start with adding this to your list...but as a "walk away" consider this instead of the 5 months of payments.
Financially, this may be a better deal for you long term, purchasing tha coverage is around $4k, I think. Not sure how Much your Payments are...so might be a wash or close.
Mentally, leaves you in a better head space, knowing this thing won't nickel and dime you over the period of ownership.
GM may like it better than writing you a check, so may be easier to get done.
However, if GM offers this, I would happily cancel the warranty (if possible) for a refund and take up GM's coverage instead.
Thanks for the great suggestion.