ok so server has been up now since about 12 minutes after the last post, and RAID is rebuilding on it.
what we did was break the RAID array and preserve one drive.
Took the drives out (and set the preserved one aside), put a new drive in its place.
Booted the server up, insured all working, that passed, then we shut it down and moved back to the rack.
Just now we have started the RAID rebuild to the new drive and it will hopefully complete soon without any interruptions.
It it on 55% now for the raid rebuild and moving very swiftly overall