I would still get a disc replacement. You might have copied it to the hard drive but you still have a bad disc, and even then who know if the disc copied properly....
I too had the clicking issue. I called Gamestop where I bought it at and they gave me a new game (the was not UPC and said not for resale just like the one that came with the system) and it worked fine after that. No more clicking and I was able to install the game were before I wasn't.