When I did mine (over two years ago) they ran through the full HR interview, and the first guys to go who had extra time also did the systems portion. I wasn't able to do it. You don't need to bring your logbooks or anything with you to the job fair, but you should be fully prepared to interview. Don't go if you haven't studied the gouges and systems.

When I did the real interview in SLC they only did about a 5 minute HR portion because I had already done it at the job fair.