Marketing List CRM 2011

Hello-

My CRM system has around 300,000 contacts.  I am trying to create a new marketing list with 400 members.  Some of the contacts may already be in CRM and some may not.  Is there a better way to add member to a list besides doing 1 contact at a time.  If I upload the system will create duplicate contacts.  Is there a way to upload the list into a funnel of sorts? Any advice? 

Thank you.