2. DO NOT SWITCH YOUR ORIGINAL HARD DRIVE TO THE SECOND PORT: I had neglected to buy Hard Drive mounting screws for the new HDD, and figuring that the SSD doesn't require as secure a seating, I decided to transfer the existing mounting screws. Ultimately, this made me believe that the original drive (the SSD with Lion installed) would work perfectly fine in the additional port. WRONG! Booting up after the first upgrade attempt, the mini took about 30 extra seconds searching for the bootable drive, then was excruciatingly slow starting various applications. I tried setting the "Startup Disk" in System Preferences to no avail. So I ended up having to do the upgrade all over, moving the SSD back to the original port. After I did this, the mini was back to its speedy self!
3. If you decide to seat the original HDD/SSD in the additional SATA port, a fresh Lion re-install will likely be required.