If you're lucky enough to have had your codes saved in your code manager on your computer, just reload that. If you entered them by hand/did not have them saved, you'll have to get the codes and redownload them. Assuming you weren't doing any dodgy hacking (pokesaving), you won't have to get too many codes.
Meh, thanks. I lost meh cord, so I have to find the Cloning code, the IV check code, fast egg code, fast hatch code, and EV'ing code(personal purposes only, xD)
BTW, anyone know the Game number for Diamond? My Action Replay got completed wiped.