Nuendo will not author a DVD. You can mix in surround and even encode the surround stream, if you bought the upgrade that allows you to, but even that will just give you a file.
Every time I've done surround, I just mixed it down to the 6 channels and handed it off to the people authoring the DVD, so that they could sync it up to video and make the DVD master.
As far as mixing in surround goes, RTFM. Like John said, there is way too much to it to answer on a forum. It is explained beautifully in the manual.