Well, now you are making things even more complicated.
You do not need 2 hard drives. You can partition 1 drive into 2 partitions and use one for your system and the other for storage. Then you can buy 1 larger drive.
You could buy 2 drives and set up a RAID. That would make your speeds much faster.
We can give you more options and confuse you even more.
Is the drive broken? You can, you just do not want too. lol
As far as what comes with the drive, it is most likely an OEM so it comes with just the drive. You will need 2 SATA cables and also make sure you have enough SATA power cables available to plug the drives into your Power Supply.
As far as which to go with, I agree that the WD is the best choice in this case.