You might want to check Rita's PMP prep book on change management.
You really need to understand on the concepts mentioned in PMBOK guide in order to answers all the questions on the exam. I would recommend you pick one of the test preparation materials/books (go with Rita book if I were you), and go through first. Then, read and study PMBOK guide. Then, you can master the change management.
I'd like to know what sections of the PMBOK need to be covered to completely understand/master all concepts related to change management. Is there any other material or resource that covers this so that we can confidently answer all questions that may arise from this subject area?