How has modern civilization impacted the spiritual lives of the indigenous people? Are indigenous religions still practiced today? If so, how have the practices changed over time?

This is an extremely broad set of questions. There are indigenous peoples all over the world. You need to as your teacher to phrase the question much more narrowly.

Even in light of my opinion, here is one response to this exact question just a couple of days ago:
http://www.jiskha.com/display.cgi?id=1184024289

Good luck!

=)