This is as important as acing all other questions. GS is a pretty flat organization, so it's all about teamwork. Show that you're excited about the opportunity and willing to do whatever to bring value to the team. They'll probably ask you questions to assess your raw intelligence, so be thoughtful/analytical about your answers.
However if you're going soon then I would not try and learn very much more that was new. One of the most common failure modes at interview is not from a candidate failing to know a particular thing, but instead not knowing things that he says he does.
Thus given a low finite time budget between then and now, I would treat your resume as the syllabus. If you say you've priced digital options, then make very sure you can do it without the text book in front of you.
The GS process is longer than pretty much anyone else, and so it is pretty close to certain that you will be quizzed on things you say you know about. No one expects you to know about everything, but if you fail a question on a topic you've studied, it looks that much worse.
Failure modes is a big thing for us in the people we counsel. What other headhunters may not tell you is that HHing is mostly the management of failure. Most people who apply for any given job, don't get it, so avoiding screwups is at least as important as doing good new things.
Also, I'd also like to share a couple of silly little errors people make.
Bankers really hate people who aren't on time. A lot.
I know for a fact that people have missed good jobs because of what is interpreted as a lack of courtesy. Maybe it comes across as disorganisation, which frankly is not better.
Please schedule to turn up around 30 minutes early, more if multiple modes of transport are involved. Do not present yourself at GS 30-45 mins early if travel things work out, but grab a coffee (or better a hot chocolate) at the nearest Starbucks, and arrive at reception 5 mins or so before the scheduled time.
The other is just as simple. Get a good night of sleep before the interview, again people manage to get this wrong with bad consequences. Good/bad sleep and affect your measure IQ by an easy 10%. There are those who'd pay me good money if I had a drug that would buy you that much improvement, but I give you it for free