I like to stay in St Helena. It is norh of Napa and an easier drive to many of the wineries I visit. I start off the morning at Model Bakery for some of thier famous English Muffins. I also grab a loaf of bread or two to snack on between winery visits. Hotel 1424 is nice, or if you want to save money, try the El Bonita Motel. It's older, but clean...and inexpensive. Restautants in St Helena that I like are Press, Cook, and Cindy's Back Street Kitchen. I also like pretty much every restaurant in Yountville, including Bouchon and Bottega.
If you want to stay in the town of Napa, check out Avia Hotel downtown. Its new, very nice, and close to lots of restaurants and bars. I like it, but prefer St Helena. It seems to have more charm.
For wineries...there are just so many. Try to visit wineries that are close to each other so you arent driving around all day. here is a link to a winery map:
http://napavalley.com/visitorsinfo/Napa_Valley_Winery_Map.pdfThis map does not include every winery but has quite a few. The Hess Winery is quite a hike up Mt Veeder so maybe try Hendry, which is on the way up. If you are going to Stags Leap, try Cliff Lede and Pine Ridge, which are close by.