To undertake such an endeavour (basically emigrating to a new country), a fair amount of research and preparation needs to occur before you leave. We began a year or so before, engaging in discussions with people (friends and colleagues alike) who had been, getting their perspectives and advice-both positive and negative.
We generally discovered from these discussions among other things, that while it is possible for single and married people to go to Korea and work, it can be quite lonely for single people, especially if you do not surround yourself with a good support network. We were also advised to learn the basics of the language as soon as possible, as in certain towns, the English language is very scarce, not to mention the massive culture shock that you will experience.
We then researched and chose the recruitment agency that would get us there, and began filling out and completing the masses of paperwork required. This generally will take months to collate, as you will have to apply for police clearance etc which takes month to get processed.
The interviews and contract signing occur not long before you leave, and so booking flights and organising the money you will need (usually enough to last you a month-around One million won) can only be wrapped up in the weeks leading up to your departure.