Changing internal IP address range in an Active Directory Network with Exchange on site

OK, here is my position:

I have a customer who is running nice and smoothly on internal ip address range 192.168.1.x but along comes a company who has purchased my customer's business and wants me to change the ip address range as it will conflict with one of their other sites. The ip address range needs to be changed to 192.168.2.x.  To be honest the range is irrelevant but what is relevant is that this customer has two Domain Controllers and an Exchange on site server.  Can someone give me the correct working procedure for this exact scenario i.e. what needs to happen and when please?

My initial thoughts were to change the DCs IP addresses and update DNS on both DNS servers then change the IP address on the Exchange box and re-boot it but I am very nervous about doing so as it all sounds a bit too easy using this process.

They are running a mixed mode Domain with a 2003 and a 2008 R2 Domain controllers with Exchange 2010 sitting on 2008 R2.

I have already have the port forwarding on the new router and also the MX record change in hand.

Any guidance would be appreciated.

Thanks Rob