Sorry, there is no one guide which will tell you all. Some programs have help file, or PDF guide file. Some you have to learn from reading forums, but if you do not know anything about DVD structure it will be a long way to go and even after all that it will be very little improvement to your sound file.
Like I said, first is to use PgcDemux to separate audio from video, than, if the audio is .ac3 format, you will need to convert to .wav format. If it is a .pcm type it does not need conversion, unless it is 5.1 audio, because most of these audio editors will work on stereo only.
Than you will use Audacity to "clean" audio. After you are done you will have to convert it back to the original format.
Once done, you use Muxman to put your new audio file together with origonal video to produce .VOD type file acceptable by DVD.
The last is to use VobBlanker to replace existing video with new one from Muxman.