Mass Effect 2 DLC Queries?

Okay Basically I have a few queries about Mass Effect 2.

I want the DLC for Mass effect 2 but i have a pre-owned copy, thus i don't have access to Cerberus Network



1 - Can Steam DLC be applied to a CD version of the game?

2 - Where can I buy the DLC if the above can't be done, and do I need the CN to do so.



Any help would be great, I mainly want the Arrival DLC, but the Shadow Broker stuff would be great too, just want to be ready for ME3 :)Mass Effect 2 DLC Queries?
1. There is no Steam DLC aside from the preorder or Deluxe items..

2. The DLC is bought through the Bioware store at http://social.bioware.com