It will work technically but you will find KT won't give you 3G service without you getting your US iPad certified first by the local communications agency just like they do with iPhones. The cost puts most folks off. Check with the KT guys in English on twitter @ollehkt_expats
It doesn't make sense but that's how it is. Do you really need the 3G model as there is a lot of free or cheap wifi access here. And ironically you don't need to get your wifi only pad certified.
Not god news but hope this helps.
Merry Christmas.