Forgot to add that maybe, just maybe LVM will handle the remapping of the Raid drives. I cannot say which way for sure - You'll just have to try it out and wish for the best outcome. Under SuSE LVM I believe it does the remapping itself and secures the data. Not sure about other distributions or LVM programms (they may all be the came generic program - here's hoping).
I'd start with LVM first and formost before taking any actions I posted previously.
Definitly read the LVM documentation completely and work out the process first until your comfortable.