[quote name='jut22']have you done this before? If this really works i'm doing it.[/QUOTE]
As long as its in the return window (i.e. 30 days on new) that you bought it originally, yes it works.
its a UPC (Universal Product Code). Meaning its the same UPC you get at local stores (i.e. bestbuy, walmart, etc) as it is at Gamestop. The only exception here is if you get some game with an exclusive for that particular retailer they will have an exclusive UPC. Greatest hits games may also have a different UPC.
If the UPC on the new game matches the old receipt then go for it, its a no brainer. (which it wil for DeadSpace 3 right now, especially if you buy your new copy at Gamestop).
And they should refund to original purchase type. so if you bought with cash you get cash, credit, its returned to that card.