I've been contemplating starting a smallish Mordor (I think) force. I would like to know more about the game before I buy, and noone near me plays (yet

), so I have come here to ask for the assistance of my fellow Dakkites. One of the driving things behind this game for me are the Nazgul (especially the Tainted and the Undying). So, here are my questions:
1. What size is a small game of the Strategy Battle Game? What size is a standard (like 1500 for
40k) game? I'm especially interested in the number of minis required and the time needed.
2. At what scale games can you include heros like the Nazgul? Is the game built that they are needed for the very smallest of game? Or are they like special characters in
40k, only coming out at the highest levels? I'd hate to get into the game to realize my favorite models are unusable most of the time.
3. What books are necessary? Aside from the hardcover rulebook, what sourcebooks would I need? Are the rules for the Tainted and the Undying in the Mordor sourcebook?
4. I understand that you can ally evil with evil in the game, are there any restrictions on that?
5. What would be a good starting purchase? Aside from the main rules plus a sourcebook?
Thanks in advance for your help.