For what I know, there's no tool for modding FFX.
Some work has been made at modding, but it is still hand-made with hexadecimal editors or light programs to automate things.
What you're looking for is very specific for tones of reasons and won't be possible for a long time if ever :
1) Sound files are a pain to decipher. If you have experience and are used to the main ways of digitizing sounds, then you can do something about it but it's near impossible else.
2) You're asking to export AND to import sounds. That will mean tones of work in order to find the place in the file to import datas (that's because the game is console-only and know only one file format on the computer : the binary image).
3) It's quiet possible that dialog sound files also contains other stuffs, like the lip sync. Anyway, there are good chances that Square sound files are custom and it would need a converter for being able to read them with normal programs.
Plus, I would guess that, with PS2 games, problems arise because you have to handle huge files of several GB.
So, no. I'm afraid no one can help you :/
