Considering how to resign from an academy: Midnight run vs. prior notice?

I have been working at the academy for a few weeks, but I am considering resigning due to contract violations and unreasonable work demands. After my trip to Japan, I plan to stay in Korea for a month on a tourist visa, but I am wondering if this plan is feasible since I do not yet have an Alien Registration Card (ARC). I have two questions: 1) Is it better to leave quietly without informing the academy, a "midnight run," or should I notify them 24 to 48 hours in advance? I am worried about causing trouble for other foreign teachers. 2) Is it possible to re-enter Korea on a tourist visa after visiting Japan? I am curious about this since I do not have an Alien Registration Card. I would appreciate opinions or advice from those who have had similar experiences.