Because I don't have Leopard yet, I don't have Xcode 3 so I can't answer your Xcode 3 questions. You can still ask them if you want, if you don't mind the response "I don't know". Apple has an Xcode mailing list where you can ask Xcode 3 questions as well as questions on other Apple developer tools like Interface Builder.
I will post on the blog when I get Leopard, also known as Mac OS X 10.5.
