Ok, as you do have a Video DVD, I can walk you through this.
1. Insert DVD into computer, start 0SEx. Now you have to check all the tabs in 0SEx:
Ti: Choose the longest title here (if there is more than one title). That will be the main programm, in your case the concert.
Ch: We'll come to this at the end...
An: Check "01" (usually there will be only one angle anyways).
Vid: Un-check everything.
Aud: Check *one* AC3 stream, un-check the others (if there are several). If you can choose between a 6 channel stream ("AC3 6ch") and a 2 channel stream ("AC3 2ch") I would suggest choosing the 2 channel stream as it will already be optimized for stereo listening (as opposed to being optimized for surround systems).
Sub: De-check everything.
Fmt: Check "Elem. Streams".
Seg: Check "Title"
Back to Ch.: In concert movies, usually each song will be a chapter. You can check all the chapters here, which will result in one long audio file of the whole concert. *OR* you can only check one chapter at a time, which will result in individual audio files for each song. This is just up to you.
2. Open MAC3dec and convert the ac3 files to whichever audio format you wish. You can convert it directly to mp3 or you can convert it to aiff (regular cd-quality audio), open this aiff-file in QuickTime and export it as aac (mpeg 4).
3. Enjoy in iTunes, on your iPod, burnt to a CD, etc.