We went to Church.
We were prepared to not understand a thing, but as luck would have it, one of the speakers was from the US, and he had a translator for the rest of the congregation. So we understood a third of it. :)
After church, we had lunch in a random nearby park, and then we decided to give Gangnam another try. We went to a different station and this time, we were more successful. (It's the one on the 2 line, NOT the 7.)
As far as I'm concerned, Seoul was a success.