Well, not too much work really. There are numerous utilities available that can convert AC-3 to WAV, so simply converting the audio from the DVD will allow you to work with it on the timeline as with any other WAV file. However, as AC-3 is a lossy codec, you’re already starting with a compressed source, so while you didn’t lose any quality in converting to WAV, if you export to any other lossy format, you’ll lose even more quality.