i'm sure their are plenty of people on these boards who lnow how to extract an ac3 soundtrack from a laserdisc.
i know that several people have used a 5.1 mix from 1997 from the special edition of a new hope, and that the audio files once were online in newsgroups and torrents and if no longer there you can ask people on these boards for help.
as for empire and jedi i have never heard of anyone using the 1997 mixes from the laserdiscs for their projects as a whole, other than taking bits and pieces like ocp movie did to recreate some of the 70mm sound mix differences.