This is how I would have done it:
Install AC3Filter (We'll use it in Goldwave)
Demux audio from DVD using DVD Decrypter in IFO mode.
Open your AC3 file in Goldwave, mark section you want to record using the left and right mouse buttons. Press Cpy2 in toolbar to save the section you've marked.
Open up cmd and use ssrc to normalize audio and convert sample rate to 44100Hz and then burn.
Be aware, DVD uses DRC (Dynamic Rate Control) so your file may have very low volume in some parts while others are very high. If you want me to I'll explain how to fix it.
MPEGs are no different form DVDs, just use vDubMod instead of DVD Decrypter.