Hello Kristin,
I can only comment to Schweinebrueck (that's part of Oldenburg, parish of
Zetel). Marx and Etzel are close to Schweinebrueck, but at that time they
were part of Ostfriesland - you could write to upstalsboom@gmx.de.
Civil records start only around 1875. You didn't say when your G-Grandfather
was born. For the church records of the lutheran parish of Zetel we recommend
to visit the State Archive in Oldenburg, Damm 43. (Open monday thru friday
from 8 am to 4 p.m.
Gerold Diers (Oldenb. Geneal. Society)