[flexcoders] Question about how to learn Flex 3

[fred44455]

I am learning AS3 with Actionscript 3 Esssential Training(Lynda.com) but I was 
told that the Flash packages are different from Flex 3 packages. Should I 
continue learning AS3 with this video? It use Flex 3 as compiler but does not 
use any <mx. packages. Will I get confused when I start learning AS3 for Flex? 
I don't want to waste my time.  Thanks for your time.