What happened to the Germans was truly terrible but understandable after the way Germans had behaved to Poles and Poland. However joining the EU has had more than economic results and in the last few years there has been a distinct thawing in the justifiable, even if regrettable, attitudes of many Poles. Most of the churches were taken over by the Catholic Church and converted to Catholic use. Places like cemeteries were simply abandoned until just recently. When in Poznan two years ago my friend took me to three cemeteries where they have cleared the forest, demarcated the area of the cemetery again and made a small central rising with a new cross and rededication as consecrated ground. Obviously most of the graves are unrecognisable but it must be remembered that many of these areas were very primitive and poverty stricken and the headstones were mostly of very poor quality - no grand marble monuments, although we did clean off a few gravestones and read the names. In Poznan itself the Bamberger German descendents have recently opened a very good museum recounting the history of their presence in the city.
A lot was destroyed but if you know the name of the town/village it would be well worth while writing to the local authority/church and asking what records they still have. Actually, although they had to choose to take Polish nationality and could not have German schools or any official use of the language, and were wise to try and hide the fact that they spoke German at home, it is surprising how many did choose to stay rather than be expelled. A curious twist of history. Best of luck with your searches.