Have custom pages packaged with my theme?

This is what I want to do:
My landing page is supposed to be a custom designed page. I want to write a template for it and put it in a file, for example landingpage.php. In my menu I will have two links: About and Blog.

I want About to lead me to another page which contains a list of pages that has been created in the admin section of WP. Also one of them will be picked as default (I will fix this from a custom options-page in the admin).

I want Blog to lead me to and archive which lists all categories and also lists the posts from all categories in chronological order (latest post will be nr.1 and so on).

How should I approach this? In what files should I put what? How do I resolve this with URLs, e.g. what will be URL to the archive page become and how can I determine it dynamically, regardless of what URL structure the user has opted for in the admin?

I have programmed WP themes before, just never anything custom like this. Thank you.