1. Yes, the boards with the game box are HUGE! and very well suited to gameplay. No one has made a replacement map. http://www.historicalboardgaming.com/ has a variant of the map, and his OWN rules… you might be able to use that instead if you really wanted to, but I don`t see the reason unless you are a hardcore custom gamer.
2. Interesting question… Global had whats called OOB or Out of Box Rules… those are CONSIDERABLY outdated. Larry Harris himself, the creator and designer of Axis and Allies, has whats called the Alpha Project, where he is changing the rules of the game, to make it just “perfect”. It’s ALOT better in terms of game experience if you play with these rules. OOB is broken.
Go here for Alpha + 3 rules, http://www.harrisgamedesign.com/phpBB3/viewtopic.php?f=40&t=6149
To be used in CONJUNTCION with the rules you get with the box! You can get those rules in .pdf at axisandallies.com
3. Yes
IN SHORT
There are ALOT of new rules, new units, and new things to consider… its going to take ALOT of time to get used to it (atleast 3 or 4 games) my advice is to get someone with some experience, and to play the stand alone` versions first… Europe and Pacific, until you get the hang of it.