Prep. Class For the Unholy GMAT

I'm in a bit of a quandary, you see...I'm in my last term of undergrad. and I feel like in order to crack a 700+ score that I'll probably need to take a prep course somewhere. Here's the qualifier: I'm out of school Dec. 7, I can't miss school to take the class, I need to fly to Chile to see my fian...