Hacking HELP. Patching NTSC-U language files into NTSC-J copy of a game?

[takaneko]

I'm assuming this is possible, if it's not please feel free to correct me.

I'm trying to patch the English from Animal Crossing: City Folk (NTSC-U / RUUE01) into Machi he Kyouko: Animal Crossing / Doubutsu no Mori (NTSC-J / RUUJ01) so that I can get the Japanese DLC, but not have to learn a whole language to enjoy the game.

I know how to use WiiScrubber and PartitionBuilder to modify the ISO, but I need some insight into what files to patch.

Can anyone help? I will make this mod available if I succeed in making it. If anyone even wants it that is.