My grandparents were German colonists who moved to Poland and then were in the Russian controlled part of what was once Poland and is Poland again. I am pretty sure for that time period Poland has the records. They took very good care of all the records they found from other countries. Napolean made sure all records were written in a uniform way, so once you learn the "form" they are easy to read whether in Russian or Polish. Most of these records have been microfilmed by the Mormons. There are websites where you can research it. In fact their website has an idex where you can order the correct microfilms.
Or you can contact the Polish Archives in Warsaw and they will pass it along to the correct archive in the region where your relatives were born and research it themselves and send you a letter with the results in Polish. There are email addresses to the Archives as well, but I did my research with snail mail so I don't know how it works with email. There is a charge for the records from Poland and it costs just a few dollars to order the microfilm, but you have to go where there is a viewer and look at lots of records to find yours.
At the top of this section is a sticky about geneology resources for finding information and records. I copied a link that if I remember correctly, it will have the addresses of the archives, churches, etc, as well as aids to reading the formed way the birth and death certificates were written.
www.maxpages.com/poland/Home