We always have pretty good luck along the Silverado Trail. I'd start there. If you have particular kinds of wine you're into, a little research beforehand probably wouldn't hurt, as some of the better spots in the valley are by appointment only. (Although that can be flexible, depending on how busy it is.)
Lots and lots of great spots to eat, especially between Yountville and St. Helena. One of our favorites is the Farmstead Restaurant at Long Meadow Ranch. I'd skip V. Sattui if I were you. Don't really care for the wine and the service is meh -- when you're in wine country, ain't nobody got time for that. It's a tour bus stop.
Sonoma is indeed less pretentious, but wine country -- in either valley -- is essentially only there to be touristy. It's like Disney World for grownups. So roll with what kind of wine you like, find some good food (not hard to do), soak in the scenery, and enjoy. Above all, avoid the snooty wine people if you can. They're the worst.
6-7 days in wine country is a little much, IMO, though. You could do easy side trips up to the Russian River Valley (also great wine, fun towns, old resort areas, a redwood grove, some great breweries) and especially Point Reyes for a stunningly beautiful stretch of coastline (check out the elk preserve at the northern tip) and pound fresh oysters all day at Tomales Bay. The oyster houses are awesome, and the feds are threatening to shut them down, so better do it while you can before they're gone. Can't recommend a day out around Point Reyes highly enough.