Well, there are a few things you should know.
Most of Korean are kind to someone who can't speak Korean, so don't hesitate, just ask anything to Koreans.
First, Korean currency is Won and pretty big number.
for example, $1 US dollar is 1245 (Won), which is one paper note of 1000 and some coins.
Korean currency paper note
1000, 5000, 10000, 50000.
I usually think $1 US or Aussi dollar is just simply 1000 Won. just ignore three zero from Korean money.
Second, Korea is very good public transport system, so you need to get map for bus and Subway, when you get there. You can get easully get map any where such as airport, subway station and so on.
Third, try to make local Korean friends. they will help you a lot.
There is more, but you can get more information in Korea.
I wish you have good memory in South Korea. about 10 years ago