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A few handy phone apps to install to make getting around easier...
I know you said your language skills are minimal, but you also said next March, so maybe you have a Korean friend who can guide you through using them. The metro and bus apps both provide real time schedules of trains and buses in both directions, and maps of stops and stations. The taxi app (which I haven't needed to use yet myself, but have installed in case) is supposed to be great - Just enter your location and send, and a taxi comes directly to you.
That might at least help get one hurdle out of the way. Seoul is a great place to visit, but confusing the first couple of times.