yeah it's really different now with actionscript. You can really easily make your whole website using only one single action layer...One thing is that the learning curve is steeper than for AS 2.0 (not that bad though).
A tutorial that has been pretty helpful for me to understand AS 3.0 is Computer Arts "Creating generative art with flash" tutorial. It covers alot of the basics. You can find it at their website.
You will also have to learn how to load external images, movieclips, etc but it's really not a big deal. Learning how to make your own classes is also important (they tell how in flash's help)
Once you know the basics you can look through the help in flash to learn new properties, methods etc.
Then the sky is the limit!