There's some truth to both camps here. On the one hand, you can't really know what law school is like until you experience it, and there's no need to get super stressed out now. On the other hand, it is useful to spend some time preparing for what you'll encounter, because law school exams are really different from undergraduate exams, and you need to have a plan going in for what you're going to do.
So, that being said, here's a ton of advice I wrote for 1Ls last semester on the topic: http://thegirlsguidetolawschool.com/law-school-exams-101/
. It'll keep you busy for a while, and explains everything from what law school exams are testing to the details of dealing with an ambiguous essay question.
I've also started an even more targeted site: http://lawschooltoolbox.com
, which will contain most of my new exam prep content (so as not to bore everyone on The Girl's Guide site!). Feel free to sign up there, and there will be lots of good stuff for you.
Best of luck. You sound very prepared, so I'm sure you'll be fine!