Please do not assume that the birds are disease-free. The stress of moving these birds to a new, even better environment may allow some subclinical diseases like polyomavirus or chlamydiosis to become active and create greater expenses than quarantine and testing for you. I highly suggest you have these birds seen by a competent avian veterinarian, and they can discuss with you what your budget allows in the way of testing. These tests will allow you and your veterinarian to make an educated judgment call on each bird based on the data, not the feeling. If the birds test normal and appear healthy after the completion of a thorough physical examination and testing, then you can consider keeping them and setting them up as breeders.
Quarantine is more important than all of the fancy testing procedures available.
Quarantine periods vary from person to person and facility to facility. Many people use the 45-day rule as a length of quarantine. I have heard of some aviaries that have a 5-year quarantine before new birds can enter the core breeding facility. Obviously, this is not an option for most of us. Ideally, a quarantine building is available with separate airflow and floor space.