If i import a personal video without sound and then import (underneath the video in vegas video) my .wav file encoded in dts or ac3 (i use surcode) how can i make a dvd compliant mpeg file to burn on my dvd-r?
Just encode the video to an elementary stream MPEG2 file (.m2v). Then, in the DVD authoring program, use the video rendered from Vegas and the AC-3 audio file - the two files will remain SEPARATE and will not be combined into one MPEG2 file.
You can also use a program like TMPGEnc to mux the two elementary streams into a .mpg to author using an authoring program (such as DVD Workshop) that will not re-encode compliant mpeg files.
Good place to look for info on this is www.vcdhelp.com. Search on "AC3" in the forums.