Buick Rendezvous Radiator Replace/Remove

My Car Showed No Signs Of Overheating Then It Shot To Red And Shut Off. I Left Vehicle At Shop Asked To Be Told The Issues. I Was Told It...

I''m Geting Oil In The Rad , What Cuold Be The Problem & How Hard Is To Replace Rad On A Rendezvous. Do I Has To Deal With Tha Ac. ...