I had this failure twice on my Macbook (before switching to a different brand drive and keeping the latest warranty-replaced drive as an external backup). I tried everything, including the freezer trick, DiskWarrior, and Data Rescue II. Nothing worked. Those drives were dead. Anything's worth a shot, but I'd say don't get your hopes up.
It's nice that they gave you the old drive back - in my case, they always wanted it because they said they had to send it back to Apple or Seagate (I forget which). I did convince one "genius" to let it spin up and physically mash the head into the platters so data would be destroyed.
If DiskWarrior were successful, you'd have a working drive/volume on your desktop. At that point, you could use any tool, including just the Finder, to copy data off of it. Like I said, I highly doubt this will happen, though. Most likely, DW (and the OS in general) won't see a drive to repair at all.
Finally, if by some miracle you do get DW to see the drive but it fails to repair due to hardware errors, I highly recommend Data Rescue II. I had a recent case of a failed drive (Western Digital MyBook) where DiskWarrior simply couldn't complete its rebuild of the directory because it kept running into hardware errors. DW is fantastic for corrupted filesystems, but only if the drive is still physically working. Data Rescue II takes a completely different approach - instead of trying to rebuild the directory to get a fully working volume, it simply tries to recover as many individual files as it possibly can. I was able to use that to recover 95% of the files from the MyBook before it went totally bad.
Good luck!