Anything you'll be working on later should be exported as DV-AVI. MPEG is not considered an editable format, but rather a final format for viewing.
DVD authoring programs convert the MPEGs to .VOB files by just adding in fast forward/reverse links and chapter points. Then they create the index tables, menus and links.
For DVD burning, Nero works fine. For authoring, NeroVision is fast and produces acceptible menus, static and animated, animated selection windows, timed buttons, but you can't make it do neat tricks like selecting different language tracks or autoreturn to next title, etc.
DVDLab Pro, $199US, will allow you to do most of the Hollywood menu tricks, if you're willing to put in the time to learn how to use it and to design the menus.
Before going overboard on the menus, just keep in mind the user will spend very little time futzing with them. That's not why he bought the DVD.
Fav quote - "Experience is whatcha don't get 'till ya don't need it no more."
System - Athlon 1.4GHz, Win98, Hauppauge PVR250 receiver and compressor.
Software -Magix Movie Edit Pro 10, Nero 6 + NeroVision Express, Moho 4.61, PSP 8.1, Bryce, Quicktime 6.52 pro, Goldwave 5, DVD-Lab.
Cameras - Panasonic GS9, Canon ES8400V, Canon EOS D20 and Canon A70