I live in Northern California and spend a great deal of time in the Wine Country.
Sonoma's OK to visit wineries. As a general rule of thumb, forget about staying or eating there. Napa's the place to be. For lodging, stay at the Carneros Inn and book time in the spa. Their Boon Fly Cafe is great for breakfast -- and they've got a really cool new restaurant called Farm. You will not be disappointed. The place draws a younger crowd -- so there's always some interesting things happening around the pool. Ask the desk attendant in the spa for some "horse cookies" then go and feed the horses and cows over by the fence. It's a hoot.
You could also stay at the Vintage Inn in Yountville. Not as nice, but very solid. Their spa, run in conjunction with Villagio's, kind of sucks, though. Their room rate includes a really good breakfast. Avoid the Calistoga Ranch. Costs a fortune and you are relentlessly paying tips because you have to take a shuttle to get anywhere -- and they make you valet park your car. That said, their restaurant, the Lakehouse, is truly amazing as is their spa. If you do stay there and do have dinner there, ask Dave, their wine steward, to make some suggestions for winery visits, etc.
Meadowood and Auberge de Soleil are both over the hill. There's a family run place called the Cottages of Napa Valley. Really cute. Sort of like a bed and breakfast. Speaking of B&B's, Deer Run in St. Helena's very cool. Stay in the separate cottage up the hill -- so you won't have to eat breakfast with a bunch of other morons talking your ear off about their great sales jobs. If money's no object, all I have to say is Poetry Inn -- where $600 a night puts you in the cheap seats. You want one choice? Carneros Inn.
Wineries. Domaine Carneros. Great sparklers, fun staff, nice view. Best sparkling wine tour is at Domaine Chandon. Best still wine tour is at Robert Mondavi. Best wine tasting is the Beaulieu Vineyards' Georges LaTour tasting room. You pay $25 for several different samples of really good stuff. Silver Oak is totally overrated and for chumps. Frank Family and Rombauer make terrific wines -- but their tasting rooms are overrun with snobs. Viansa's awesome. Go around lunch time, get a bottle and have lunch on their terrace. Hess Collection has a really cool winery with a great art collection. Chateau Potelle's neat, too. Really small -- yet their VGS Chardonnays and Zinfadels are world class.
Food. Boon Fly at Carneros Inn for breakfast. Rutherford Grill for lunch or dinner. Everything else, like French Laundry, Martini House, and a few that I can't think of right now, are loaded with snobs.
If you're stocking your cellar, don't buy in Wine Country. The winery prices are really high. Go to K&L wines in San Francisco or, better yet, Beltramo's in Palo Alto. I shop at Beltramo's. Their prices are great -- and if you explain the kinds of wines you're looking for -- they'll set you up with a nice series of bottles. Here's an idea: talk to a buyer about getting a few magnums of a hearty red wine from the 2007 vintage. That way, you can cellar it and open them on your 5th, 10th, 15th and 20th anniversaries. Of course, they won't be for sale yet -- but do explore for planning purposes.
Wines I like right now: Domaine Carneros Brut and Le Reve. Best in class and reasonably priced. Orin Swift's Claret "The Prisoner." A $60 bottle that sells for under $30. Get it now before they get found out and totally overrun. St. Francis 2004 Old Vines Zinfandel. A $50 bottle that sells for $15 at the right places. ZD's 2004 or 2005 Chardonnay. Pricey at $30 or more, but, when properly served, is absolutely incredible. If you want to spend, you really can't go wrong with Far Niente Cabernets. Forget Opus One and Screaming Eagle. Overpriced. I really like some of Beringer's higher end wines, too.
I could go on and on -- but I've got stuff to do. Good luck.