How can I edit scenes of a DVD and then re-burn it while maintaining quality?

I'm trying to help someone out who only wants a few scenes from a movie (for academic purposes). How can I import the movie, edit it, and then burn it back while retaining the highest quality possible? Right now, I'm using HandBrake and iMovie HD. Is there a better alternative? I'm only interested in free software or advice on what settings to use with the aforementioned programs. Thank you!