I've been dealing with our son's ADHD for seven years now, so here are my suggestions:
1. Take your questions away from general parenting sites. Not everyone here has experience with ADHD, but you'll find plenty of people with "opinions" about it. You'll get a lot of garbage advice, comments about it being overdiagnosed, etc. Instead, seek out ADHD boards. Good starting places are DailyStrength and ADDitude magazine.
2. Join CHADD right away and look into attending local chapter meetings or the national conference. Terrific group for those dealing with ADHD. It will help you filter through all of the science and non-science/scams/useless advice.
3. Subscribe to ADDitude magazine. It covers all aspects of life with ADHD. Super resource.
4. No kind of diet works best with ADHD. It's a brain disorder. I looked into this, hoping to avoid medication, but there just isn't any research showing diet makes one iota of difference. Still, always good to feed your child healthy foods.
5. If your pediatrician really understands ADHD, stick with her. However, it's generally best to have treatment managed by a psychiatrist. They specialize in conditions like ADHD and know all of the latest research and treatment options.
6. Don't fear medication. It isn't evil. Our son went from being kicked out of preschool and having one friend to fitting in at school and having friends. Concerta has been a godsend. At 10, our son made honor roll all year. That would be impossible without medication. It allows him to be his true self.
Just keep in mind, though, that it can take some trial and error to get medication right. Also, it doesn't last all day, so whatever ADHD symptoms you face will not go away entirely. You'll also want to meet with a behavioral therapist for advice on dealing with the hellish parts of the day.
7. As far as school, you'll want to ask the school for an evaluation for an IEP or 504 plan. An IEP will apply if your son has problems affecting his performance. A 504 plan will give special accommodations that help him excel in school. For instance, our son's 504 plan gives us an extra set of school books at home, so when he forgets his homework (as in, every day), we have what we need at home.
8. While you're at UC Davis, pick up information from the UC Davis MIND Institute. They're studying ADHD there and can offer some good resources.
Best of luck as you start this journey!