NVX Volume C Life Support

Last night I discovered that two of the four disks (numbers 3 and 4) in my NVX have gone bad. I attempted to shut down the NVX as precaution while the replacement drives were being ordered and shipped. When I went to check on the shutdown, the power button was blinking and the display had the message "Shutting down... Vol C lifesupp!". When I checked again this morning (approximately 10 hours later), the blinking power button and shutdown message remained.

A couple of notes before the questions...

- The device is over 5 years old (so out of warranty)
- It is running 4.2.15 and X-RAID2
- Each drive is 1TB - but only 7% was used at the time of failure
- The important data is backed up in ReadyNAS Vault

And...here are the questions...

1) If the shutdown message is still there when I get home tonight, should I force the power off via the switch on the back and then attempt to restart?
2) When the replacement drives arrive, should the power be on or off when I install them (I'm assuming I need to do one drive at a time here)?
3) Should I disable backups (via vault.readynas.com) until the system is stable again?

Thanks in advance!

- Dave