Cisco has upgraded its CCNA exam to 607, while I'm stuck with a 507 textbook. I have had little experience with networking before. Is it a good idea to buy a new 607 textbook to prepare for the cert exam, or should I study off the older 507 book? The text that I'm using right now is called "CISCO CCNA 2.0 Certification Exam All in One" by Robert Larson. Thanks.