Well, you've asked for a couple different things. If you've edited your show 16:9 HDV and you want a dvd that will play on a standard ntsc tv, out put a quicktime self contained movie from FCP, open up iDVD 6 and use the file you created as the movie. iDVD 6 will do the downconvert and all, and you will end up with a letterbox image, black bar across the top and bottom, that will play on a standard dvd player. If you want more contol than that, take the same file you out put, import it into FCP, start a new sequence, make sure the settings are for standard ntsc and drop your file onto that timeline. You will now have a nice red bar above your footage that will require you to render before you can "print to video", but this way you can ajust before render to what suits your taste as far as cropping the image goes.
good luck,
kevin
"A problem can never be solved by the same consciousness that created it"
Einstein