I have a RAID-1 configuration, and my RAID card died. I'm using drive 1 only until the new (identical) RAID card comes in. Can I just plug in the new card when it arrives, if some of the data on disk 1 has changed but disk 2 hasn't? Do I need to clone disk 1 onto disk 2? Or is there something else I need to do to refresh drive 2 when the new card arrives?
Find and read the detailed manual for your RAID card. Many RAID1 systems have good tools for detecting that the two component drives have different data, and then helping you to specify which is the "correct" drive, then update the other drive to match, thus re-establishing the RAID1 array. But you really need the manual to find out if your card can do this, and how to use it for that job.