Can't tell if replacement drive is doing anything.

Hello NetGear folks,

I'll try to keep it simple. I have an older ReadyNAS 516 with 6 x 2 TB drives setup in a RAID 5 array. The thing has been great, and while I know it's in its EoL, it works just fine for my needs. Recently one of the drives died, so I found a replacement 2 TB drive, I believe unformatted (forgot to check before but the vendor I purchased it from said it was unformatted). Now the NAS is running in a degraded mode and I have no redundancy. 

After swapping out the dead drive for the new one, nothing is happening. I understand the resynchronization process can take a while, but it looks as if nothing is happening at all. There's no note on the admin page about the sync happening, and the bay on the Volumes tab looks empty, like there's nothing there. When I open the front panel, there is a blue light on the bay where I replaced the drive, so this makes me think it's maybe doing something, but I just can't see any kind of note in the logs about the sync starting or the drive being present. Only the blue light on the bay. 

So, here are my questions: Does the replacement drive need to be formatted before hot swapping? Is there an easy way to see if the re-sync has begun, and/or how to monitor the progress of the re-sync? Should I avoid reading or writing to the NAS in its degraded state? If it's working in the background and I have no way or monitoring it, I don't want to strain it.

Looking for some help here if anyone can provide any insight. Thank you in advance!