Buy it
direct. The conference CDs of the conferences for the last 10 years is only $99. Contact the seminary and ask for the bookstore.
Honestly, I must say that I have used these books for all kinds of things - they are more relevant than alot of the conference material that is out there. For a small seminary, GPTS puts together some good conferences. And they are cheap too.
The best book I've used in the series is the one on Sanctification.
Chris.