Two plus months later and the WD external drive attached to my SA 8300HDC is working fine. Just noting this in case it will help others with their SA 8300HDC. It's at 30% full now and I do a fair amount of recording, including recording two programs at the same time. It's been a while so I can't say for sure, but to connect, I went with this procedure:
0. I did not format the WD Caviar drive or change any jumpers. I just installed it into the Vantec fresh out of the box.
1. Unplug the SA 8300HDC.
2. Connect the external case to the SA 8300HDC using eSATA, and power up the case.
3. Power on TV so you know when the process is complete.
4. Plug in the SA 8300HDC, and power it on.
It takes a few minutes to recognize and format the drive, and no indicator lights on the front of the box are helpful. Eventually a message comes on the TV indicating success. I think this process took 5-10 minutes for me. If the 8300HDC is powered on but there seems to be no progress, hit the 8300HDC power button or the channel up/down, as it may need a power cycle to proceed.
I hope this helps someone out there struggling with external storage.