Migrate DHCP from 2008 to 2012 - Maintain same Hostname and IP

I have two servers, DHCP1 and DHCP2 running on Windows Server 2008 and I want to migrate them both on Windows Server 2012 without downtime to the DHCP service. After reading a few articles this is what I have so far.

1. Export all the DHCP configuration from the 2008 server using "netsh dhcp server export C:\Users\user\Desktop\dhcp.txt all"
2. Import all the DHCP configuration on the 2012 server using "netsh dhcp server import C:\Users\user\Desktop\dhcp.txt all"
3. Authorize the new DHCP server from the DHCP console.

My problem is that I have to maintain the same hostnames and IP Addresses for the 2012 servers. So I’ll have to bring down one of the 2008 servers, replace it with a 2012 server and import all the configuration I exported from the 2008 server. And then repeat for the second 2008 DHCP server.

1. Will I have to de-authorize the first 2008 server before shutting it down and replacing it with a 2012 server?
2. Will the second 2008 server work properly when the first 2008 server is replaced with a 2012 server?
3. Anyone who’s done this before, do you have any advice, tips & tricks or anything I should be on the lookout for?

I realize this should be a simple task, but I’ve never done it before and I’d like some advice from someone with more experience.