Study as3.0?

How can I study the changes in AS 3.0 from 2.0?
I know AS 2.0. But I don’t know to define classes in it. All AS 3.0 tutorials start with “this is a tutorial for beginners…”.
But didn’t help me actually. All contains some packages and classes. Is there anything other than this?

I have some problems learning AS 3.0 because I know some AS2.0

Some of them are:
How do I play or stop the _root timeline calling from inside another movieclip.
In 2.0, I know it is _root.gotoAndPlay() or _root.play(). This won’t work in AS3.

How to make a simple preloader for the swf using the ENTER_FRAME event?

I want some nice easy tutorials to migrate into AS3. Do you know some which shows these types of differences?