The first thing you need to do is figure out what religion your ancestors were in Sniatyn. Each religion recorded their own birth(baptism), marriage and death records. If you can figure that out it will save some time looking through film. In any event, here are the steps:
1) Go to http://www.familysearch.org
2) Click on Search then Catalog
3) Do a place name search on “Austria, Galizien, Śniatyn (Śniatyn)” ( you don’t need the special characters)
4) Click on church records
5) There will be listings for: Catholic, Greek Catholic, Armenian, Evangelical ( Lutheran I think) Metrical books.
6) Choose a religion and click on the heading
7) Print what you see Take the printout to the nearest Family History Center and pay to get a copy.
When the copy of the film arrives, load it in a reader and start looking. I’ve been looking at catholic and Greek catholic and most of it is in Latin. I’ve found the book “Polish Roots” by Rosemary Chorzempa to be very helpful with reading the records.
Good luck! Let me know if you need more help and especially let me know what you find!