mp3s come in 1411 kbps? 320 kbps is about the highest I know of, so that might be a wav file, in which case, it's pretty easy to do (lame encoder, and a front end if you want to make it a bit easier. I recommend EAC.)
If it really is an mp3, you can decode it to wav, then re-encode to whatever quality you like. It would then be a transcode, but it's not like you're planning on selling it.
http://www.exactaudiocopy.de/http://lame.sourceforge.net/