The exam is definitely do-able coming straight out of school. In fact, when I took the class, I had no experience in Incident Handling. I was familiar with most of the tools from messing around at home, but I had not professional experience with them.

You will get out of the class what you put into it. My suggestion would be to go on SANS website and look at the topics for each day and start reading, experimenting with those topics that you are the weakest in. The more knowledge you bring into the class, the more you will get out of the class...

While you're at the conference, GIAC will likely offer a SANS at Night talk on the certification process. You should definitely attend that. They give some great advice on preparation for a GIAC exam.

Good luck!