It would be up to them to prove your maintenance or lack there of was the reason it failed. That isn't going to be easy with a log that follows their recommendations.
Not sure how much it actually costs to install but I assume around 2 grand, maybe I'm off but my electrician didn't seem to think it was a big deal this summer when they updated my circuit breaker. Since I told him my plans he installed a temporary box and the conduit leading to it that would be replaced with the transfer switch come time for install.