Finally! I can now play MP3s under Ubuntu.
I spent entirely too much time on this. This was the first time I installed an application on my own. I first attempted to load EasyUbuntu but never could get the downloaded codecs to integrate with the existing applications. Specifically, I wanted to be able to run MP3s through Google Reader and the RhythmBox Music Player.
Tonight I decided to take a different tack on the problem. I figured that there had to be a way to install these codecs via the command line. After some extensive searching on Google, I found help on installing restricted formats. I followed the instructions here and once I was complete, everything worked fine.
I did notice that when the process began the installation process noted that I already had some of the packages installed. I presume this was due to the many attempts with EasyUbuntu. What was missing was the integration which was successfully completed with this process on restricted formats.