Researching the Czechorowski family 1. Open

My grandfather Stanislaus Czechorowski, was born in Nieborzyn, Greater Poland Voivodeship in 1915. He had one sister, Pelagia, who married a local farmer, Stefan Szczepankiewicz and had many, many children beginning in 1930. My father says that in September of 1939 my grandfather was picked up by the Russians and taken to Russia as a prisoner. He eventually escaped the Russians but was caught by the Germans and sent to France to be slave labor. He escaped the Germans in France and joined the Resistance, and met my grandmother (who is also Polish). As far as I know he never went back to Poland. My father grew up in France until the family relocated to New York. My grandfather rarely talked about his family, he had had a very hard war. I knew nothing about them until recently when a woman in Poland got in touch through myheritage.com and was able to find the graves of his parents and sister. Since then I have been able to find out very little, I must have many cousins, and also would like to find out more about the history of the family. The surname seems to be unusual. Most of my Polish DNA is apparently from Southern Poland, which is confusing (my grandmother was from Eastern Poland, where I also have a lot of DNA). I would love to be able to look at church records where he grew up and also in Budzisław Kościelny, where the graves of my great-grandparents and great-aunt are. I’d also like to see if I can find anything about his war experience, though I realize that may be very difficult. I would appreciate any pointers or advice.