Get a book on collecting Korean furniture, read and understand it, and all the nuances that you learn. Understand how to recognise age, and quality, the different timbers, the evolving styles of hinges and locks, the nails used. And how to recognise the large amount of fakery.
Then visit Seoul, visit a few reputable dealers, and buy it there.
p.s. i used to be pretty clued up on antique Japanese chests. There is NO way I'd buy ANY '''antiques''' in this country. Almost all of it is fake, or patched together.... simply not worth bothering with.
p.s. Something like this...
http://www.amazon.com/Korean-Antique-Fu ... +furniture
Even a little knowledge will hugely empower you.