zombiewhacker, good morning.+1
I've used it to clean up multiple MP3's in my collection.
Once you've tweaked the file, you'll need to Export
the file (you won't see a Save in the File drop down menu) as an MP3 (or from a slew of other options, i.e. AIFF, MP2, Ogg, etc.) and once you've selected that you'll see an Edit Metadata window where you can tweak all sorts of stuff.
Once you've done that, the file will be exported and then you may have an option to "Save Project As" which saves (I believe) all your workparts.
It's not the easiest program I've ever used but it's free and works well.
Plus, if you do get stuck the FAQ at their site (http://manual.audacityteam.org/o/man/faq.html
) is pretty helpful.