Alas, "a class" is not a source. I've also taken quite a few classes here in the University of Iceland regarding old Norse beliefs and Middle Ages in Iceland, but what I name as my sources are the texts we studied there. My professors are of the opinion that these texts are still the best sources that we have and that archaeological findings support them, such as the finding of Egill Skalla-Grímsson's homestead.
Egils saga too was most likely written down by a Christian scholar, Snorri Sturluson, but Egils Pagan practices and even his blood sacrifices were still written down and described as effective, and everything in his saga states that he really was capable of magic. There is even a mention of a goddess taking a side in a battle, turning it for the worse for the other side.
And I have to repeat myself a bit here because it feels a little bit like you're twisting what I say into something that I never said: when it comes to Finnish Pagan beliefs I'm not talking of tossing a coin in a well. I'm talking of having a sacrificial table for a god, or a hiisi site, and going there to pray. People certainly believed they were Christian, but some also blended in other types of worship that went much against Christianity... the difference was that many ordinary people didn't see a contradiction in situations where priests would see many. For this reason I don't see any problem with Minna bringing Christianity in to the SSSS world and see it as a logical continuum of the past.