Most businesses I know would not preserve or worry about preserving the computer name and IP. There should be no need if the network is setup properly.
Otherwise, I would swing it - setup a temporary DC (it can be virtual), transfer AD to that, demote the original DC, rename it and give it a new IP, then install the new server with the old name and IP. Once installed, transfer AD from the temp DC to the new server and demote the temp DC. Once demoted, remove it from the network and copy the files off the original server.
Though really, it's a LOT less work if you just use a new name.