Some of the things from the DIT study guide were super-helpful for my exam. Other things weren't, but that's the nature of the test... not everything you study will be on there.
Basically, you should learn it in as much detail as they tell you to learn it. They know more about the test than any of us. If they say it's a 4-star topic, make sure you know it. If they just briefly mention it, then you probably just need to know it superficially.