I suggest that you start from what you already know and make use of the online sites like ancestry.co.uk that should be able to identify other researchers either UK or Gdansk based, there is no point just turning up in Gdansk and expecting everything to be accessible and extant. Make a detailed research log that would identify which specific records, ecclesiastical or civil, that you may have success with. Research any local family history groups in that area and make contact with them to find out more local information from researchers living locally. use the forums on rootweb to see if anyone has any advice on other online resources that will help you plan your research and identify and understand the sources.
Try to contact the local archives in Gdansk to ask for information on local burial grounds and where parish records etc are kept and what is the access.
look for links to sites that may help like this one:
http://www.cyndislist.com/poland.htm