April 19th, 2013, 2:53 pm
I vaguely remember making a sound pack for Italy Mafia (that i have stored online somewhere).
I remember using Audacity to convert the audio to mono and then converting it to an .ogg file i think? You also have to cut the sounds so they match up in length with the original sound you're replacing to prevent horrible sound bugs, like camera noise rain. There was also a program I got from gtaforums that allowed you to extract the sound files and compress all the sounds back together.
tl;dr it's a lot of work, you'd probably be better off getting a sound pack.