There should be no handling fee for withdrawing money with your card in Korea, right? Our country can't use it, and foreign countries may also support international credit cards.
If you change won, just go to the Bank of China and bring your ID card. It's best to go to a bigger branch. Some small branches will have more US dollars, Japanese yen and Hong Kong dollars.
You can only change it into cash and you can't take it out of the deposit card there. . Cash is a little more expensive than cash, but it won't be much worse.