Hi,
Something does not make sense.
users /accounts/ pages and setups for UMP are stored in the database.
if you ump server is redone then installing a new one and pointing at the old database should have you
back up and running without an issue.
the only way I see you loosing everything is if your UMP is installed on your database server and you are loosing your database.
If you are loosing your database you will need to work with your DBA on a backup and restore plan.
You can export pages and setup from the control panel in UMP to re-import them to a new server of the same version.
You might want to check out the liferay forums and documentation on this as UIM does not have that on our site.
the only thing that should be lost if you lose your ump would be some setting in the portal-ext.properties files
possibly a custom logo or images.
If you can provide a little more detail we might be able to provide better direction.
hope this helps