Actually RAID 1 is what you want in this situation.
You can either swap a new drive in for the old one or attempt to format the bad drive and re-mirror using it. If it was simply corrupted a format may fix it, if the drive is shot you'll need a new one. Just follow the RAID instructions so you don't lose the data on the good drive.
edit: From the looks of your message it's the first drive that's having an issue (0).