Changing IP Addresses

We have 5 Servers. One is PDC and others are BDCs. Before I joined the company I am currently working for, someone had set up the IP addresses to be using 10.10.10.1 to 10.10.10.100. Now my boss wants me make changes and let it start with 192.168.2.0. Currently we have 2 Routers. One is in the main building and the other one across the street in our other building. It connects to us through T1 line. We also have another Offices in Maryland and Canada that access our database. What exactly doI need to do to make the changes go smoothly? What exactly do I need to change and what exactly do I need to retain? I don’t really want to screw things up. Where can I get additional assistance? Help!!!