The currency in Germany is the Euro.
It is rather uncommon to pay with credit cards in Germany and many stores do not accept them. However you can withdraw cash with your credit card at every cash machine. At the Kirchenplatz (5 minute walk from the IOW) in Warnemuende there are the OSPA (Sparkasse) and the Volksbank which provide ATMs. Also there is a Postbank Counter in the local post office. 300 meter away in the Muehlenstrasse also the Deutsche Bank provides a cash maschine. Banks (open Mo-Fri) will also exchange money, though they sometimes charge a fee to do so if you are not a customer.
Computer / Internet
At the TZW (Technologiezentrum Warnemünde, main venue) and at the Leibniz Institute for Baltic Sea Research (Icebreaker Party) will be computers available to access the internet. Moreover, there will be WiFi available, for which the password will be provided at the conference reception desk.