What should I expect during background investigation?

First off, I made it past the oral board interview for the deputy sheriff position I want—yay! Definitely the part that had me the most nervous. Next is the polygraph and background investigation phase.

I have a very clean record, good employment history, etc. The only thing I’m kind of nervous about is the fact that after I received my Associates degree I basically just stopped attending my next semester of classes, so I’m sure those will show up as did not complete or fail on my transcripts. Is this something to sweat over? :/

What all should I expect during this phase? What do they ask references, etc?