Some of the answer can depend on which DVD recorder made the discs. Can you tell what recorder made the discs?
The rule is Womble MPEG-VCR works great for anything under 2 hours (single video file, not full DVD length). Single videos longer than two hours, use Womble MPEG Video Wizard. For discs made on a Panasonic recorder, use MPEG Video Wizard and be sure to change the audio option to MP2 when saving (the Panasonic AC3 files are fubar for editing).
For decompiling the disc, use DVD Decrypter
in IFO mode, be sure it's set in the options to extract to a single VOB file, do not break it up. By default, the software breaks at 1GB chunks.
Quite of bit of this info is found in guides at www.digitalFAQ.com
If you need help finding any of this software, PM me.