Adding 2000 Server Domain to an NT Domai

I am adding a new 2000 domain to my organization. Some users from an existing NT domain will be moved to the new domain. Users being moved to the new domain will still need to access resources in the old NT domain.

What would be the best way to move these user accounts from the NT domain to the 2000 domain without recreating them and re-applying group memberships?

Also, would manual trusts need to be created for the moved users to still access resources?