move gw 8 to gw 2012 questions.

This system as about 100 mailboxes and only a primary domain (secondary will be added after this transition). I have a gw 8.0.2 running on a DOMu and the data for that system is stored on a separate partition. I have installed gw 12.0.2 on a new DOMu on the same host as the gw 8.0.2 server. I also have another server that is running gw 2012 webaccess. The 2012 system is running and functional as a test system. Now I want to point the 2012 server to the 8.0.2 data. All the servers are linux with the gw8 on a sles 10sp3 box. The others are sles11 sp 2. Below are the steps I am planning on using to do this.
1. Using C1, change the agent settings for GWIA,POA and MTA so that their path will be the new path to the partition where the ver 8 data is located.
2. Stop the agents (GWIA,POA and MTA) on both the gw8 and 2012 servers.
3. Shut down the gw 8 and 2012 servers.
4. Configure the 2012 server so the partition that has the GW 8 data is mounted by the 2012 server.
5. Start the 2012 server, which should start the gw services. (am I correct that when the 2012 agents are started they will update the gw 8 data to function in a gw 2012 environment?)
6. Change the IP address of the 2012 server to be the same as the gw 8 server (this just makes it clean).
7. Change the configuration of the webaccess server (SOAP and DVA) so that it will access the change I did above. ( the reason I am not changing dns is that some of the clients have the gw 8 srvr as an ip address, so I have to do both, change ip address and dns entries)
8. Test.
Is it necessary to do a top down rebuild?
Let me know what I am missing. This is a production system and I want the change to go as smoothly as possible. Thank you,