To say Scott Brick is a great narrator does not give the man his due. Scott is active in all areas of the audiobook world, including helping talent break into the business.

Check out "Scott Brick Presents: Share The Experience, A New Contest To Find — And Employ — The Audiobook Industry’s Newest Narrator Or, An Audiobook Narrator Celebrates His Tenth Anniversary By Inviting Newcomers To Come Along For The Ride." a title long enough to almost qualify as a short story in itself.

So, do you want to take the challenge but wonder how to record an mp3?  One way is through a program called Audacity.  The challenge will be in configuring Audacity to convert your audio .wav file to .mp3, the audio format required for submission.  To do this you will need a second program called LAME.  The good news is that the process is well documented.

Most likly your computer has a microphone that can be detected by Audacity.  Though the sound quality may not be the best, it's a good way to practice.  On a step above, you might consider a USB mic.  They have come down in price and sound pretty good. 

Another alterantive is simply to go to a recording studio.  If you're in a bigger city, chances are you can find a place within budget for a couple of hours of recording time.  After all, you'll only need a 3 minute read.  The advantage of this comes when it's time to process or edit the audio.  An engineer can take care of this quickly with the correct tools.  Plus, it's a great opportunity to get a feel for what it's like to be, 'on the other side of the glass.'

Good luck!