I randomly took the PCAT over the summer (I used to be pre-med, so it was pretty random...). It was my first time, and I had only 2-4 weeks to study for it because I was bombarded with summer class. Luckily I had a lot of pre-req classes under my belt and I'm strong in some areas than others, but I definitely DON'T regret taking the test (had it scored).
Of course, I didn't just blindly walk into the test room... THAT would be stupid. I DID freak out probably the entire month and tried my best to cram everything. Although I never took a Kaplan course, I used my friend's books and basically read every single page of every book (except verbal; I took my chances and assumed I was more verbally capable than when I took the SAT's...).
After the first test, I knew what sections I had to work on (chem), and which sections I had to pace myself on (reading comp, chem, math). But thanks to all the cramming/studying that I did do, I walked out with a decent score considering the circumstances. I took my second (and last ever) test two months later. Again due to a full course load (19 credits) I had 2 weeks of intense studying... I mainly concentrated on chem for those weeks, flew through bio book just as "review" a few nights before, and skimmed through math book for equations and review on derivatives/integrals the night before. Either I was really lucky, or the random cramming sessions helped me out because I ended up with a nice score!
Freaking out is normal. Just don't make it cut into your studying time
And as much as it may help to take it the first time to "get the gist of it" or whatever, you obviously don't want a bad score either. Try to put in some studying time for it, good luck!