How would i go about making a music uploader / player or were could a get a script that does that? I want the user to be able to listen as well as contribute music to the site..

you can just let users to upload an mp3 file using an html form. You can even allow uploading more than one file at a time.

Then on a server side you need a script that would store the uploaded files in an organized way and add entry of file name and its new location (a path to where it was saved) to database.

The good thing about mp3 files is that they can be streamed from streaming server, so you don't need any extra steps to encode them for streaming.

The last step is to setup a streaming server. There are several open source free streaming servers. I personally worked with 3:
Red5, Darwin (from apple) and Helix from real networks.

all of these support streaming of mp3 files.

The very last step is to embed the HTML code that would start streaming a file. That would depend on which server you choose, every server has some simple instructions on how to embed the HTML code.

I know this probably sounds too complicated.

You can just place a link to mp3 file directly without using any streaming server. That would work too, especially for relatively small mp3 files.