Easy answer is clone the drive to a new one.
But first... When you say brink of death do you mean its failing or its just full? If its almost dead, you may have an issue with transfers in general and should back up to an external drive asap while you sort out the process of going to a new hard drive. If its just full, you can use that later as a storage drive, cuz why waste a perfectly good 1.5TB of storage.
You're running a modern(ish) system so I'm guessing you have a SATA drive. Pick up a new one of you're desired size and make sure you have a SATA cable with the purchase (provided you don't have spares floating around). SATA 1, 2 or 3 are all the same connector, just different speeds and are cross compatible so go with what your budget allows. You're going to need to have both hooked up when you do the transfer so make sure you can put the drives in your case.
The easiest way to transfer would be to clone the drive over to a new hard drive. There's a bunch of options out there, Symantec Ghost is one of the oldest names in the game, Acronis supposedly makes a good software set, but there are freeware options as well if you're tech savy and dont mind playing with some linux distros and utilities. If you check out http://www.pendrivelinux.com/
You can find some good utilities. I personally use the Yumi installer to make bootable utility USB drives that have things like drive cloning tools. The Yumi tool helps you download utilities in the process so its super simple.
To clone it, you're going to need to follow the directions of the software but the basics idea is this, by cloning you're making an exact copy of the old drive on to the new one. All data, settings, etc will transfer over. If your 1.5TB drive is full, its going to take a few hours to do. Once its done, swap out the old drive with the new and you should be able to boot as normal. You can then use the old drive as a storage drive (provided its not dead), just make sure in BIO its not listed as the boot drive and then wipe it clean so theres no chance of problems.