Some useful gazetteers for Prussian Poland are:
Uetrecht, E., Meyers Orts und Verkehrs-Lexikon des Deutschen Reichs (Meyer’s gazetteer and directory of the German Empire). Leipzig: Bibliographisches Institut, 1912–. (FHL book 943.E5mo; film 496640–41; fiche 6000001– 29.) This gazetteer lists places alphabetically, gives their former German province, and states whether a place has its own parish or synagogue. It also indicates the location of the vital records office.
Gemeindelexikon für das Königreich Preussen (Gazetteer for the Kingdom of Prussia). 13 vols. Berlin: Verlag des Königlichen Statistischen Landesamts, 1907–09. (FHL book 943.E5kp; film 1186701, 0806633–35.) Volumes for each Prussian province are arranged by district with an index at the end. The gazetteer is in German Gothic print. Information is given in columns and includes population figures as well as civil and ecclesiastical jurisdictions.
Former Prussian Provinces or parts of provinces that are now in Poland include Schlesien, Brandenburg, Ost and Westpreussen, Pommern and Posen.
The volume numbers for these areas are as follows:
Schlesien v. 6 film 806,635 item 3
Ostpreussen v. 1 Film 1,186701 item 3
Westpreussen v .2 Film 1186701 item 4
Pommern v. 4 Film 806,634 item 4
Posen v. 5 Film 806,635 item 3
Brandenburg v.3 Film 806,635 item 1
Here is a diagram showing the column headings in German and their English translations:
To help you located parishes, both Lutheran and Catholic as well as civil registration offices for Hannover, please use the Gemeindelexikon Hannover, FHL number 943 E5kp v. 9. It is also on film 806634 Item 2.