You definitely need a visa if you're going to be staying for six nights. These can easily be obtained through a travel agent, who can do all the paper work for you. In my experience, all you need is the visa application forms, a passport-sized photo, the fee, your actual passport and a Proof of Residency form (which you can get at the immigration office). Give these to the travel agent and they'll mail the documents to the Chinese Embassy to approve the visa for you.
Please note that since you're currently residing in a country for which you are not a national, you need to fill out two application forms. One is the actual visa form and the other is the Supplementary Visa Form (which must be filled out since you're not a Korean national). They can both be found on this website:
http://www.china-embassy.org/eng/ywzn/lsyw/vpna/rap/t84254.htmAnother thing is that it's really good to have the details of your trip organized before you submit the application form. The form asks for your flight and hotel plans, and many people actually book their hotels and flights before they apply for the visa (just so they can have this information to put down). However, some people say this is a bit risky as there may be a chance that the embassy declines your visa and you're stuck with these bookings. YET, this is really unlikely to happen especially if you don't have any real fundamental reasons for why your application would be denied (as long as you're a tourist from a country that is not in conflict with China, and as long as your travel plans seem genuine, there should be no reason why your application will be rejected).
One last super important detail- make sure you have
6 months or more validity left on your ARC card. You cannot obtain a Chinese visa in Korea if your ARC expires in less than six months. It's a rule they made a few years back and has been a huge inconvenience to people who weren't aware of it prior to booking their hotels and flights.
Have a good trip!
