Hop over to the GTA Vice City page on GameFAQs.com
, there is a handy FAQ there, about halfway down the page, titled 'Music Ripping Guide' by Splintax, you need to click that link.
[I would directly link straight to the FAQ but unfortunately GameFAQs do not allow direct linking to FAQs and Guides listed on their site.]
Basically, you download a couple of programs. Dont worry, I have done this; the programs are secure and not anything dodgy. The original audio files are on the game disk, and can be accessed simply by putting the PS2 disk into your computer. However, they are of a format which is totally impossible to play on a computer, this why you need the programs, to convert them into something your computer can play.
You put the disk in, and use one of the programs to convert the files to wave format. [This is the format that Audio CDs are made in]. You then get some very large .wav files [each about 500MB], which you can use the other program to convert to mp3s, each being about a tenth as small as the wave files -about 50-60MB each. These are then compatible with any mp3 player.
This method also allows you to extract and convert to mp3 any audio file in the game, from sound effects to mission cutscenes [audio, no video]. It is a kinda long method but as far as i know is the only way to do it. I have copies of the radio stations on mp3 on my computer, but don't expect me to send them to you because I have dialup and it would take ages. [well over ten hours if you're wondering.] It is much quicker if you do it yourself, as I did.
NOTE: This method only works for PS2 versions of the game. There is a link to a PC version of it on the site, but no way to do it from an XBOX game disk.