We experienced a few more failures so we bit the bullet and started the repair on Friday. None of the automated tools for backing up and cloning the array would complete, so we manually mirrored everything overnight and our tech swapped out the hardware on Saturday afternoon. Because the swap would mean we would only be offline with 10 minutes and the a tech was available right then, we just did it. (Our apologies if you tried to visit Windlyn at that time.)

Bottom line: Everything is installed, up and running, and no errors for the last 24 hours. Yay!