How do I replace audio in MPEG2 (DVD) files using Freeware?

[semmel]

Hi,
usually I would spend more time searching the forums (I did a quick search of the guides and didn't find what I was looking for), but I don't have time to do that today - sorry

I am using a capture card to capture videos in DVD quality as .MPG files.
The source unfortunately is mono on one channel, so I have to manually extract all audio, normalize it and copy the left channel into the empty right channel, then save the file as audio.

This part I have managed to do - Adobe Audition can extract MPEG audio.
So now I have MP3 files.

I have been using MPG2CUT2 to cut out the clips I need. In some cases the resulting clip is not working properly (e.g. audio can't be imported etc.), so I am also wondering if there is a freeware alternative for this, too.

But the main question is:
What freeware program can I use to replace the existing audio in the .MPG files with the new audio I create in Audition?
I don't care if it has to be WAV or MP3, I can always change that.
But I need a one-program solution that can replace audio in an MPEG file.
Batch processing would be a plus, but that may be much to ask in freeware...

Thanks a lot for any suggestion!

[poisondeathray]

MP3 is not compatible with MPEG2, you can only use AC3 and MP2 audio

There are many free multiplexers (e.g. muxman, imagoMPEG-muxer, DVDAuthorGUI, about a dozen others in the "tools" section)

[semmel]

Thanks a lot, I'll give those a try!