Help with site architecture using WP3

I am new to WordPress 3 (actually WordPress itself) and I need some help in setting up my WP3 so that later I don’t have problems. I’ll describe my site as I imagine it in my head. I need some pointers and instructions (like links maybe) that will help me achieve this with WP3. If you can give a partial answer, that is fine too.

1. I have WP3 installed on the root folder of my domain: https://www.mydomain.com. My site will contain lots of articles and some basic knowledge (beginner’s area) of my area. It is going to cover 3 geographical regions (US, UK, AU). I am planning to create https://www.mydomain.com/uk (for UK specific articles/news) and https://www.mydomain.com/au (for Australia specific news etc.).

2. I am planning to use Google Webmaster’s tools to specify that the https://www.mydomain.com/uk is intended for the UK geographical area and similarly for /au. This means the G WM Tools will consider them as separate sites.

(a)The problem I find here is how to make the beginner’s articles (which is a lot of articles) be common to all three -> .com, .com/uk and .com/au without actually duplicating the articles for the uk and au subfolders? Duplicating them will create a problem with Google while not having them come under /uk and /au would make these sub-sites very incomplete. I was wondering if I can achieve this effect by cleverly using ‘categories’ in some way? Not sure though.
(b) Would I then need to create separate sitemaps for each of these sites? How can I create a custom sitemap for these sites?

3. I want the first page of my website to be a static page instead of the latest article/post. How do I achieve this?
By the way, my website will have more of a conventional look rather than a blog -> Many of those beginner articles are timeless, so they won’t carry any author’s name/date of posting etc/comments too. But I want them to have the ‘share this’ plugin. If it is possible, I’d like the first page of UK and AU sections to be static as well, but if not having them so saves me a lot of trouble, I might want not having them so. Of course I would also want to create articles that have more of a “current perspective” so I’d consider them more as blog pieces rather than normal pages. (Once again these might be common to all three sites).

4. I want to customize the horizontal navigation bar at the top (that contains “About”, “Contact Us” etc) to contain “Foundation Series”, “Vacancies” and each of these will lead to a custom created page. A few of them might even lead to just ‘category’ pages.

5. How do I give custom titles to navigation stuff like ‘Categories’ , ‘Archives’ and create my own sidebar menus like those?

6. Is there any built-in support (or plugins) for WP3 that will help me give an e-course for visitors who register with them email id?

I guess that was a very long post. Thanks a lot in advance for taking the time to respond. Greatly appreciated.