If you don't
have too go to Napa, there are alternatives, just as nice and a lot less $. And also not burnt down.
You could stop in Livermore off the 580 and hit a couple places there on your way to the Sierra. There are 50 wineries to chose from and some of them are spectacular, i.e. Wente, Concannon, Murietta's Well, but there are also smaller places that are less well known and outstanding.
G