In reply to mloskot:
I think flying with RyanAir to Skavsta Airport is actually better than to Arlanda. Arlanda, Stockholms international airport is actually pretty far off, pretty close to Uppsala (so N, from actual city). Where as Skavsta is in Nyköping, some 150 km closer to Västervik.
Easiest option would prolly be flying to Skavsta and renting a car. But I'm sure train+bus -option is also possible.