For OpenAL tutorials, you should have a look here.
http://www.noeska.com/doal/tutorials.aspx
There is an OGG playback tutorial that will explain how to stream and decode audio from your harddrive. This will almost work the same for MP3. You only need a different library for decoding. I believe I have some sourcecode for that (taken from a tutorial, but I can't find it now).
Edit: I noticed that one of the tutorials DOES cover MP3 briefly. It uses the mpg123 library. Have a look at that.
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