I ordered the microfilm tape through a local LDS Family History Center. Here is the website for finding one near you. http://www.familysearch.org/eng/library/fhc/frameset_fhc.asp
I was lucky to have a friend who is a LDS and she put me in touch with a center, drove me there and helped me through the ropes. They also have staff at these centers more than happy to ehlp you find your records and learn as much as you can. You want to make sure they not only hhave a microfilm reader, but also a printer/scanner - not all centers do. I was able to get a printed copy (.25/pg) or save a copy of the record to a jump drive.
Find the record again on the Poznan Marriage Project, click on the parish name and it will give you all the microfilm tape numbers. You'll want to order the tape that contains the marriage dates for the year you are looking for. The LDS Family History Center will order that tape for just the cost of shipping - $5.60/tape. They keep it on file there for 1 month and you can go back and view as often as they are open in that time frame.
Be prepared to do a lot of scrolling! The marriage record I wanted was on the last 1/4 inch of the tape. There were several other parishes listed so make sure you know your parish. The nice thing about the Posnan Marriage Project is that they tell you the record number and the year. Mine said record #7 in 1860, and once I got to the right parish, there it was! It's fascinating to see all those old records, but as I mentioned above can be a puzzle to figure out. The microfilm also contains baptisms and death records but these for the most part are not indexed. I did find this site on-line too that is a searchable index of nto only marriage but birth and death records. Unfortunately for me it didn't have my parish indexed yet.http://slupcagenealogy.com/