Okay, This is part of my investigation, for those who are interested on changing DMC3 sounds.
HOW TO CHANGE DMC3 IN GAME SOUNDS? - BETA TUTORIAL v1.0
1.- Look inside the folder DMC HD Collection, there´s a DMC3 folder, and inside, there´s a dmc3-0.nbz file. Rename it "dmc3-0.rar"
2.- Now you´re able to see what´s inside. Take a look at all the "snd_XXXX.pac" files. They are the ingame sounds. Extract those which you´re interested.
3.- Now those snd_XXX.pac files, must be extracted and packed. For that purpuse, search "Pac tool update 7" of James. (You need Python 2.xx, not 3.xx installed) When you´ll extract the files, you´ll have a new folder named "snd_XXXX", inside there´re the extracted files.
4.- Now you have some snd_xxxx.ukn files. These are the sounds files. They are on .vag extension. Don´t worry, dont need to rename them.
5.- Use MFAudio for converting and reconverting purposes. Open your .ukn file and remember the herzs of the audio file. In this case, they are 22050hz. Convert them into .wav
6.- Edit them with some audio software, but remember the herzs, you must save the new with the same ammount of herzs.
7.- Open the wav file and convert it into a .vag file. Remember the herzs, write them down, and select "mono" of "Stereo".
8.- Now, rename the file into .unk and repack the "snd_XXXX.pac" file. Copy and paste the pac file inside the "snd_XXXX" folder. and run the python file for repacking purposes.
9.- We have a new snd_XXXX.pac file, now, insert the new file inside "dmc3-0.rar" and rename it to .nbz.
Enjoy the change. I know this tutorial has some flaws for example, the are some vag files with 10 sounds and you´ll only can edit the first one with this tutorial, but I will update it in the near future.