I've been there too
Did you go into the museum at all? Huge Korean War exhibit in there as well as exhibits covering the entire history of war in Korea, dating clear back to stone knives.
No, but it gives me another reason to go back if I return to Korea some time.
I didn't get out there until pretty late (it was maybe 6-6:30), and it seemed like the main hall was closed. I also missed the chance for the little tour of the South Korean gunboat replica (from a ship in a 2002 incident) which is only at certain hours of the day.
It was spur of the moment. Monday-Wednesday was glutted with a conference and cocktail party stuff. Thursday morning I walked up to Namsan Park, but had to do an interview in the hotel lounge in the afternoon. I was wiped out, but after some rest I felt like "Crap! I'm only here one more day really, DO something!"
So I saw the memorial marked on the Hilton's fold out map, and just made up my mind to ride the subway a couple stops there. I think the stop is called "Samgachki" or something; I think I could've gotten to an exit or stop closer to the memorial on a different subway line.
I just brought my main digital camera, my iPod Touch and a half bottle of water. I found myself wishing I'd brought a snack.
They do have several vending machines.
The subway is now very English language (actually, multiple language, in terms of the fare card machines) friendly in terms of signs, audio messages on the trains, and voice prompts on the touchscreen fare card machines. It's still a bit intimidating in terms of the sheer # of stops in Seoul, and sometimes the number of exits at each station can be a bit confusing to a newbie. There's locator maps on the walls near the exits, I just found that each was sort of rotated differently than the next one, and I'd get disoriented.
My Korean uncle helped me get a very useful English-langage fold-out subway map late Friday, and I think I'll feel a lot more confident about going to all sorts of places next time I visit. While I'm used to doing most sightseeing with family/friends, the War Memorial was the kind of thing I was glad to see solo and just take my time going through it.
While they discourage you from going "up" things (don't climb on top of the Sherman, etc.) I didn't see any "don't touch" signs, and there are not a lot of guards there at the hour I was there. You could go up and touch tanks and planes and stuff and not feel like some museum police squad was going to pound on you.
So it's kind of a different feel than seeing planes/vehicles inside at Smithsonian type facilities where it's more "look, don't touch."
I've considered going to Texas to visit the National Museum of the Pacific War (http://www.pacificwarmuseum.org/index.asp
) some day. I might have to buckle down and do that some day. Life is short.