Root PDC installation

Basicaly i need to do a brand new reinstallation of the root PDC for the company as far as i am aware this means all the child domains will need to be demoted and joined to the new root domain.
but a colleague tells me that all we need to do is recreate the root domain with the exact name as before and this should allow the domains that were joined to the previous root domain to connect. is there any truth to this? As far as i know this is not possiable. As well does anyone know if there is a way of migrating users for new installations?