You should be fine, you meet the requirements: http://www.systemrequirementslab.com/cyri?gameName=dayz&itemId=11929&p=r
I don't know about those reqs because I have heard that DayZ can be hard to run even on higher end systems.
Well the game hasnt been optimized yet. So yes, some high end pcs may not have perform as well for DayZ. But you do meet the requirements and I do think you will be okay.
Just turn the settings down. A mix of low-med settings possibly at 1080p. Never had that specific card so my experience is low with it. The 7770 is still a very budget card and you might want to consider an upgrade if you start playing more demanding games. Your cpu is fine considering it is an i5, so no upgrade is needed there.