NT4 Domain Question

We are in the process of moving a network to a new location. I have a NT 4 PDC server on Domain (A) and moving the main domain (B) to this new location. Domain (A) PDC has a lot of shared files and some programs that are critical. What is the correct procedure to make domain (A) PDC the BDC of Domain (B), then change file permissions to groups on the new domain (B). Domain (A) could be removed. Is this possible? How? If so, what would the effect be on the file permission for domain (A)?