Simply demux the MPEG when it is on the computer. Convert the audio to WAV. Edit in a audio editor. I like to use
SoundForge 6 for all my audio work.
Then save the fixed WAV file. Re-convert as desired (AC3, MP2, DTS, leave as WAV, etc). Author with video.
Okay, maybe NOT so simple. But it's not hard. Just a little time consuming.
There are ALSO some hardware audio devices that can be used for "live" audio work (sort of like a proc amp is for video). However, I have never wanted them. Costs too much, can just as easily spend time in
SoundForge.
Unlike video, audio encoding is very fast, especially on modern P4 and AMD+ systems. I was editing audio on a pro audio card by in the early 90s on a 486 system. And it was fairly fast back then too!