Two Domains

I have a windows 2003 AD domain.  I need to change the domain name and also upgrade from 2003.  I am in the process of setting up a Windows 2008 AD Domain.  I will setup full trust between the two domains and slowly move resources.

Can I setup the new domain with IP address from the same subnet, so I would assign for example 10.168.100.50 - 150 to the Current domain and 10.168.100.151 -254 to the new domain?

Let me know if there is other ways to do this.   I have limited resources.  I have licenses for 2008 not 2012  and my hardware do not support 2012.

Thanks,

Bill