I know many things have changed between 2012 and 2012 R2 and you will need a course or book with the updated information.
I believe they have a free Server 2012 R2 course on Microsoft Virtual Academy. It is the MCSA 2012 R2 domain review course. I am not sure if it has all of the material needed to pass the exam, but it can't hurt. It is FREE! It also has practice tests at
the end of each chapter. http://mva.microsoft.com
Larry King MCTS