i think scoring 23 on the pat section right off the bat indicates you'll do just as well, if not better with continued practice, on the real dat.
i started taking the achiever tests without really having studied from the guidebooks beforehand and was doing horribly on the science sections.
after studying though, my real dat scores turned out okay. so don't be discourage by your current scores, but they don't really indicate what your real scores will be.
those science sections benefit the most from studying, i think. the pat and rc sections you're either just innately good or otherwise (though it's possible to improve, just not as drastically as science parts).
all my opinion, though. good luck.