Eat a can of beans and an entire bunch of bitter greens every day. That covers most of your vitamins and minerals.
Some exceptions apply: Sprinkle flax seeds on top for omega 3s, use iodized salt for iodine (seaweed is high in iodine but also high in bad heavy metals), get fresh air and sunshine for vitamin D, pick out your favorite source of vitamin b12. I believe you'll still need potassium.
For exercise: A good place to start is to walk and bike for transportation. Read this book if you're wanting to be convinced that exercise is a magic pill: Spark: The Revolutionary New Science of Exercise and the Brain
My conclusion, after reading the book, was that the author knows what test results you need in order to prevent or reverse cognitive decline, but he is no expert in how to get those results. Feel free to ignore whatever he says about how you optimize your test results, but I trust him a lot more on what happens when you have successfully optimized those results.