[CentOS] Using two subnets to change network configuration

Problem:  My network uses the 192.168.1.0/24 network.  Since is the most common network in all of the world it begins presenting problems when I want to set up vpns, or try to do 
other routing.

The solution:  Change the network from 192.168.1.0/24 to 172.24.24.0/22.  This is somewhere in the middle of the less frequently used RFC-1918 20 bit private network range.  My 
network contains 40 or so nodes, windows, linux, and proprietary operating systems of various types (TiVos, iPhones, iPads, TVs, BluRay players, WAP's, etc.)

What I would like to do to minimize down time would be to create a single new machine on the network with addresses on both networks and set up as a router between the networks.  
That way, I can convert the machines one at a time, and not loose any connectivity. When all done, take the temporary router down and just use the new addresses.

Machines are set up both static and DHCP, and there are some virtual servers running on a VMware machine.  Updating all of the machines using DHCP can be done in a single pass, but 
the static machines will have to be done one at a time.

Can anyone give me any pointers to web sites to help set this up. I know how to set up multiple addresses on the same NIC (eth0 and eth0:0).   After that, I'm at a bit of a loss.

And Yes, I know setting up multiple subnets on the same physical wire is a bad idea, but this is only for a couple of days until I can get everything moved to the new address scheme.

Thanks

Harold