If I understand your question correctly, you wish to replace an existing ESXi host and you won't be making any changes to vCenter.
kb.vmware.com/kb/1010839
This KB article covers the steps to re-assign a license. You won't have to edit any databases. If you need to migrate VMs over to the new host you can do this:
1) Attach the new host while it is licensed with the 60 day eval.
2) Migrate VMs to the new host
3) Shut down the old host and remove it from vCenter.
4) Re-assign the license as shown in the KB article.