"Court action" just means filling out the common form used in all EU member states for the European Small Claims Procedure. Enquire locally for details on how Sweden implements the procedure. You pay a small fee and send it to the local court. You only have to fill out the bare facts - that EU261/2004 mandates payment if a cancellation is notified less than 14 days, which you can clearly prove by enclosing a printout of the notification email, and a printout of your e-ticket.
They will take it from there. No lawyer, no hearing necessary.
Alternately, you could get any of the multiple websites that offer to chase airlines for compensation on your behalf. I won't recommend any of them because I don't have any direct positive experience of any of them, but many operate on a no-win, no-fee basis.
However - given that your case is so clear cut, there is no way EK can defend not paying, so you should persist yourself rather than getting an agency to do this work for you . Be short and precise in your letter. Only if they refuse again, should you bring up the fact that you will resort to the small claims procedure.
http://europa.eu/legislation_summari.../l16028_en.htm