Extending 1.x vs plugging 2.x?

Do I have this correct?  We did alot extending on 1.8 and are looking to transition to 2.0.  The "how to extend" tutorials were very useful.  

Do you have a basic guide for plugging?  
Is this the preferred method to extend in 2.0?

Please note that NopCommerce 2.0 is running MVC 3 now and what you did to extend NopCommerce 1.8 will most probably require some decent effort to port it to NopCommerce 2.0.
Maybe your best bet will be to start off with the Pluralsight MVC videos here:

http://www.asp.net/mvc