Regarding the NAG Veterans Association. Contact: Clarence "Korky" Korker
He has basically taken over. He published a new Pointer, the Armed Guard news letter a few years back.
You can also post up a question on my FaceBook group, US Navy Armed Guard WWII - Group. https://www.facebook.com/groups/715188522376466
I am not finding any photos of the SS Walter N Christiansen. It seems to me like it was a "standard" liberty ship (if such a thing existed LOL). A good example might be the SS Jerimiah O'Brien berthed out in San Francisco. I posted a message on a Facebook groups page to see if they had more info.
I am NOT the expert in researching military records. But your best bet is to start with the DD214 form. Check ancestry.com also. They might have info if you have a subscription.