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!