If you mean 'renamed', just rename the groups in the NAB and let your adminP process find/fix the group names across all dbs (assumes that you have an admin server defined in your ACLs).
If you need to do it manually, the designer help has some good examples for processing the ACL. Use them as starting points.
I believe there are also a number of 3rd party tools that manage ACL's also; since this is a merger, why not let the buyer pay for the process?
Good luck with your buy-out; I hope it works well for you.