trust relationship and sites and services

Guys,

In a lab, when having a trust relationship between 2 dc's, do i need to add the second DC in the sites and services parts of AD?

Also, when i would like to replace the second DC with its own domainname9the other company) through a RODC in the domain of DC1, but i want the active directory structure, shared folder,... available at the second DC migrated, how should i do that?

many thanks in advance