OK, It's now about 23 hours later. I want to update my progress.
The actual physical 3 TB HDD swap-out with the original 1 TB HDD was a lot easier than I expected. I decided to plow ahead and see what happens after the installation and rebooting.
I put the Snow Leopard OS install disk in and booted up.
This was the scary part as it took nearly 7 minutes for the OS Install disk to be recognized and another 2 minutes for the new HDD to be recognized. (I actually broke sweat waiting).
Once into the install mode, I went straight to the disk utility and formatted the new HDD. Once formatted, the OS install only took about 17 minutes. I was overwhelmingly releaved!
Ok, install done, system rebooted, now went to Time Machine back-up to restore my iMac to it's pre HDD swap configuration.
WOO-HOO!!
My advice is just go for it, but be aware that waiting for the system to recognized the new configuration is excruciatingly painfully slow. But it WILL recognize it.