I chose to stay at MyeongDong for my 8 days stay in Seoul. At first, I wanted to so much to try the AirBnB but the room that I wanted to book was taken by someone during my stay. So, I opted to guesthouse as I wanted to feel the crowd too.
From Incheon International Airport to MyeongDong takes about 1 hour time with 43 mins travel time required from Incheon International Airport to Seoul Station, the biggest transportation hub in Seoul.
Travel with AREX is cheap, it costs me about W4,900 to reach MyeongDong and you can use the T-Money card to tap and travel around. It is cheapest option to reach city. It is very convenient too. But be prepared that you have to carry your luggages around in the subway as elevator is rare. To compare this AREX with KLIA Express in Malaysia, this AREX is spacious, long trains and fast.
Similarly to Singapore MRT, they have all the stations indicator and announcements in most common languages to make sure every travelers can understand it. Besides that, their train stations have both Korean words, hangul (English translated) and Chinese words. It is very easy to navigate around after you get familiar with it. You can find the train systems map at almost each of the train doors.
I traveled a lot to Chungmuro if I am heading down to Gangnam area, otherwise, I can easily walked to Hoehyeon station where Namdaemun is located. Some of their stations are located quite closed to each other that you can just talk from one station to another station, either by the roads or undergrounds. Do opt for underground walkways, there is where the shopping heaven is.