why are you looking to stay in Walnut Creek? there isn't really anything to see there except a mall...stay closer to SF if you want to sight see.
sonoma and napa are about an hour apart, so make sure you include that in your plans.
I would recommend V. Sattui winery (free tasting) its on the 29 in Napa. That is the most popular area for wine tasting. Also just down the road is Peju Province, which is beautiful and good wine.
If you want to try some of the smaller family wineries, try the Silverado Trail (Mumm's sparkling wines is there). Miner winery is also very good, nice small family vineyard.
As for places to stay, bed and breakfasts are always great. We had our reception at the Gaia, and while I had some problems with them (not anything to do with the rooms though), their rooms are beautiful and its pretty affordable (it's in American Canyon, which is right on the 29 but about 15-30 minutes away from the main winery area)
have fun, let me know if you need more info.