I have gone from NTSC to PAL in the past… it can be done.
There are two ways to deal with the frame rate differences: interpolated rendering or “cheat”. I did an interpolated rendering going from NTSC to PAL, 29.97fps -> 25fps, in Vegas. After some experimentation, I used some high quality settings, let Vegas do the rendering, and it took just over 8 days. But that was a few computers ago.
The “cheat” is for going from PAL to NTSC. Simply put, you lie about your video and claim that it’s 24fps, not 25fps, then do a 3:2 pulldown render — or in Vegas terms, render to “NTSCFilm” (23.98fps) rather than plain NTSC. This will slow your sound down by 4%, so if there’s music or anything really sensitive on it, you can do a pitch-neutral length conversion in something like SoundForge.
I imagine, if you simply change your PAL DVD project to NTSC and tell it to render, Vegas will render it, and you’ll get SOMETHING. The big problem is that if the render isn’t smart enough, you’ll see weird interlacing effects and other problems. But that’s the easy one to try, assuming you have a way of viewing NTSC DVDs (I know pretty much every DVD player in the UK will play NTSC, sometimes output as “PAL-60”, not sure about elsewhere out your way).
-Dave