Regarding your first question, about replacing "shift" with "change": I think you're correct but only if "serious" was deleted. "Serious" doesn't sound like the right adjective here. But I think "shift" is better because it implies a more gradual or subtle alteration.
Regarding your question about the preposition to follow "change":
I've wondered about this too. The only answer to this question that I've been able to find is over on the Chicago Manual of Style's online Q&A:
The difficult thing about English is that there is almost never a single right preposition for any noun:
-a change to the house
-a change in the situation
-a change of heart
-a change for the better
-a change since yesterday
A linguist might be able to explain why these usages have become conventional and are not interchangeable, but most native speakers of English learn them intuitively, without being able to articulate the reasons. If English isn’t your first language, lots of practice reading and listening to English is probably the best way to train your instincts.
Although I'm not a linguist, I agree with this answer. After thinking about all the examples in the list above, I don't see any consistent pattern. I think it's just a matter of what sounds natural to a native speaker.