Demuxing and Muxing FFX?

Hi guys, this is my first topic in this forum and I really need help :D

I love the Final Fantasy series (huahuau, well, I think if I didn't, I wouldn't be here...) but the versions out of Japan has terrible dubbing (why Tidus sounds like a Backstreet Boy???), I just can't stand this dubbing, but unfortunately I can't read japanese, so this is what I'm trying to do:
Demux the FFX: International and FFX Jap. From the Japanese version I get all the voice sounds files and transfer them to the FFX: International,muxing it in a new DVD,so, this way I can have the Japanese audio and the English menus.
Can anyone help doing this? 'Cause I have no clue about how to do this =\

Thanx:p

...you lost me at 'demux' xD

I'm not quite sure if I can use "demux" in this case, but this is the meaning:
- Muxing is when we get all the files we need and add all of them into a only one file for creating a DVD (in DVDs for movies they're the .VOB files)
- Demuxing is the opposite of it, its when we get this file from the DVD and extract all the files from it, so we can work with them

I don't know if I was clear enough...my English sux xDDD