That wire should do... but that is a switched wire, meaning it turns power on/off with the key. You'll probably also need a constant power wire. Get a test light, and find a fuse with constant power, whether the key is on or off, and tap the wire and run it to the other wire to provide constant power for your clock and station presets and such. You can also run a wire straight to the battery, but that's not the "professional" way to do it.
Basically, the only wires you'll need is a constant power, a switched power (which you already have) and a ground (which you should already have)
You'll probably want some speakers other than stock too. Lots of people have put some 4" or so speakers in their door panels... but good door panels are hard to come by. A good, cheap setup would probably consist of some 6x9 speakers in enclosures behind the seats, and maybe some tweeters hidden around the dash.
