Rebuild a drive in RAID after failure

I work at the University of Kansas, and after Sunday's storm, the campus was completely thrashed, including one of my servers. It's a G4 with 10.3.9 running on two hard drives in a mirrored RAID. Somehow during the storm, one of the drives failed. How do I go about re-initializing the drive and getting it back to into the RAID? I'll try it using the existing drive, but I may have to swap out the bad drive. Thankfully, I haven't had to do this before, but I want to make sure I don't mess anything up when I do it.

Any words of advice on this? I'm hoping it will sort of take care of things as soon as I choose to initialize the replacement drive.