i have some albums in mp3 that are kind of bad quality...they're live recordings and rehearsals and the volume is low and there's a little back noise. Can i improve the sound a little or am i lost since its a lossy format?

You can clean your files a little bit using Audacity or something like it. Then you can make them louder using MP3Gain.

But if they are bootlegs then the quality won't improve much, regardless of format.

Hopefully it is obvious that if 'improved quality' is what you are after you should stay away from mp3. Not because mp3 is so bad but because each time you go there you lose something more. To work on the files in Audacity, or any other audio editor, your files will, of necessity, be decoded. Save them as .wav before you start any work and save as .wav each and any time while you work on them. If you are committed to an mp3 result, don't encode to mp3 until you are satisfied that you are completly done and won't be making any more changes.