Media Monkey is a good program for fixing your music library. It will auto rename and update your id3 tags from folder name, file names, or from the web. It can scan the info from amazon and fix the id3 tags and miss-spellings very easily and there is even a free version. Anyone who has a lot of mp3's will be thankful for this program once you use it.
First thing to do is scan your music directory, then you can just tag your files or albums, right click and say auto tag from web. It will search amazon and find a match. If it doesn't find the right one, you can manually change where is searches from or manually type in just the artist name and then look though all of there albums until you find the right one. If you still can't find it, there is also an option to auto tag from file name. I prefer to let it find it online so I know they are all named properly. It can also re-encode any music file type to mp3 in very high quality (it is adjustable). It can download the album cover if you like when it auto tags and even embed it into the mp3 if you want. Be careful because large album covers can slow down how fast your med can display them on screen when you open a new directory or move to the next page. You may want to save the album cover as a .jpg and scale it down. Then you can manually have media monkey embed the small resolution pic into the mp3. It can also analyze all your mp3's and volume level them so you don't have to keep turning your avr up and down. Here is a link so you can check it out. The free version should work fine for most people unless you need the options the gold version gives you. http://www.mediamonkey.com/download/