I'm not up on all the details, but from what I understand they are dropping all the TCSEC/ITSEC stuff and replacing it with Common Criteria stuff completely, amongst other changes. I think the ISC2 website has more details. You might as well get it over with now. A month is about right for studying I think. Any more and you'll burn yourself out, any less and you won't be prepared. I started studying abougt 6 weeks prior, but ended up being lax due to the weather getting nice. There is a test on May 31 in Dayton. Go get yourself the Shon Harris book, and maybe the dummies book or sybex one as a secondary source. Given your job, you probably know most of the material already, so with a month to study you should be able to pull it off. You have your CISA already right?