Travelling to South Corea, you need a passport, valid for six months at least, when you leave the country. Return air-ticket could be required as well.
The citizens of European Union can travel to South Corea without entry visas. This fact is valid for all sorts of passports, for time period of 90 days (three months). Nevertheless, this fact is not valid for the trips when you are seeking the job.
The Immigration Officer on the airport could limit your length of stay in the country, according to the purpose of your visit. On arrival to South Corea, you are obliged to fill in the respective arrival as well as departure immigration card (you receive it just in the plane, before landing). In case of short term stay in the country, you do not need to prove sufficient quantity of financial means for your stay.
The citizens who intent to stay in the country for longer period than 90 days, or wish to be employed there, are entitled to ask for the respective entry visa at Consular Section of Corean Embassy abroad. The person who wishes to work in South Corea, is obliged to get in advance the respective working permit for Corean Court of Chancery before his arrival to South Corea.
Information and warnings on travelling abroad is to be found HERE.