I was tasked with setting up Git for my office. We have several sites. I just set up a network drive for us to push our changes to. My question is: Where do I init the Git repos
You probably want to have a centralized server which you push changes to and clone from. This server may have one repository or many. I recommend reading http://sethrobertson.github.com/GitBestPractices/ which has several sections of direct interest. Specifically picking a local workflow, a distributed workflow, and how to divide your work up into repositories.