As it's been already stated, we lack good sources from medieval times that wouldn't come from people of the Church (who surely wouldn't write about such things) or traveling merchants (who didn't have enough local knowledge).
This way I'll go with the source from 1543, which is a book by Mikołaj Rej, called "A Brief Discussion among Three Persons: a Lord, a Commune Chief and a Priest". Maybe this will help you somehow.
Unfortunately I have no idea where to get English translation of it, and translation software won't help you, as it's written as Old-Polish language poetry.
In this work, three representatives of different states speak about their rights and problems with other states. As it's really a long thing, I'll translate some parts that would be crucial for your topic - the beginning of Commune Chef speech, when he's asked by a Lord what he thinks of the Priest, who is accused by a Lord of being lazy and greedy:
My lord, we're just a simple folk, What can we know about it, poor souls? We can only believe that it's in our best interest, Whatever he says during his lectures.
(context: we don't know much about religion, we're just told what to do)
After those words he speaks of how the Church takes more and more money from the poor, while the Priests don't teach them much about the God itself. But let's go further to his summary of the quarrel between a Lord and a Priest:
A Priest blames a Lord and the Lord blames a Priest, While for us, simple people, the problems come from both of them.
(context: so we really don't care about it)
Just take it into account that the writer was not only a politician, but also Calvinist and his works reflect his understanding of the Catholic Church.