Rail Pass Check

I will be traveling to Japan for my first time this fall and just want to throw some questions out and check my itinerary.

First of all, if I get the pass, then do I still need to get a ticket for each individual ride or do I just show the pass?

What if I want a reserved seat? (I am familiar with Europe Rail passes, but not Japan's.)

I see that the Green Class offers snacks. What if I want a meal? Or a drink?

So, here is my planned itinerary:

1. Narita to Nagasaki - 2 days in Nagasaki
2. Nagasaki to Sapporo - 2 days in Sapporo
3. Sapporo to Nagano - 2 days in Nagano
4. Tokyo/Narita

And finally, I know that many people say that you don't need a ticket or a reservation, but I like knowing my plans in advance. How can I build an itinerary?

Thanks.