If you want Extras and Menus etc, well for the Menus, just play the movie with WinDVD and as the menu is shown, hit the Camera, then save. You now have a JPG file that loads into TMPGenc DVD A. As for the extras, work out the length in time of each and encode each separately. Let say the movie was 90min long, one extra at 5min and another at 10min, total of 105min. Therefore when you encode the main movie set the CD length to (90/105 x 4400 =) 3772, the first extra to (5/105 x 4400 = ) 210 and the last extra to 420. The 3772+210+420=4402 so it will all fit to the DVDR and each bit will be of equal bitrate (quality). The menus dont take up much room really. For more complicated authoring thats needed here I would suggest either DVDLab or Maestro, TMPGEnc DA is for simple authoring like when you convert an AVI for example (as far as I'm concerned!).
If the Menu is an animated menu, then it normally resides in the VTS_0x_0.vob file, Just use DVD2AVI, load in that file ONLY, use the slider to mark it out star & end. Save Project,(this saves out the *.AC3 audio) load the *.d2v file into TMPGEnc, set to Video only, load in the PAL or NTSC Template (depending on format) set to Highest Quality (Slowest) and then hit run. A couple of min later you will have the video ready to include into your menu with its audio. You MUST use DVDLab or Maestro here.
Hope thats clear.