I need help with tools or advice to create mods Thread

Hi guys, i need your help about mods. A friend and me want to begin a project about dub on videogames. I want change the voice actor or voice narrator of any game, and use the voice of my friend. Only that. How we can create this? It's difficult? What program can we use? Exist any tutorial for this? I'm so f*****g noob about this, sorry. I hope u can help me, any help is welcome.

Thanks in advance.