Well, thanks for the links. But... I think I've found the problem. It's a NAS device, connected over ethernet, plugged directly to my router. I've designated the drives to be formatted as AFP, but they are not formated as an OSX volume. Disk Utility doesn't see the drive (or any volumes), so I can't format it.
One of your links indicated the only way to do this was to connect the drive directly to the Mac via a USB connection. The drive has a USB port, but that's seems designated to be used to attach another USB drive. I have a feeling Disk Utility still won't see the drive if I hook it up. May give it a try.
Again, I had to drop a little hunk of code in to make the one drive function with Time Machine. This was easy enough, the Buffalo firmware offers a simple check box. When I did it, the drive (or actually 'server') downloaded something briefly. I'm assuming it was a specific driver.
NAS devices are great, but a word of caution to potential buyers - they are not completely plug and play if they are not Apple manufactured.