The main language spoken here is Korean (한국어 han-guk-eo), and the alphabet is called Hangeul (한글). It is quite easy to learn.
The standard language is referred to as 표준어 (pyo-jun-eo) and is the main style of intonation used in Seoul, in language classes, in books, and in television. This is probably what you would hear if you watched a Korean program or news announcement. Just like in America where we have the "Boston accent," "Texas accent," or the "Southern accent," certain regions in Korea speak differently. These regional dialects are called 사투리 (sa-too-ri). Their intonation and region-specific vocabulary can vary greatly to the point where a person from Seoul (which speaks in pyo-jun-eo) has a hard time understanding what a person from Busan (which uses 경상도 사투리 gyeong-sang-do sa-too-ri) is saying.
A dollar is to the United States as the Korean won is to South Korea. Perhaps it is more accurate to refer to it as the South Korean won, as North Korea has their own version of the won. Paper currency consists of 50,000, 10,000, 5,000, and 1,000 bills. Coins include denominations of 500, 100, 50, and 10. For the time I've been in Korea, the exchange rate fluctuates more or less between 1,050 - 1,200 won to $1.
