Change IP address scheme Win 2003

I am running a Windows 2003 Small Business Server and am using a 192.168.0.x class c network. I have lots of trouble using vpn because the 192.168.0.x network seems to be very common so I want to change to something else. My first question is what is a good one to use that would be a little less common? Second how do I go about changing my network to using something else? This server runs DNS, Exchange, VPN, and is the DC. I tried moving to a different set of ip addresses on a test network and could not get DNS functioning again so my Active Directory was all screwed up. How can I do this to get everything up and running again? Thanks.