Hi,
There is no way to really export just the private key and certificate, which can be reimported into the ACS.
However, what you can do is perform a backup of the database. This will save the registry that includes the certificate and the private key. Then you can restore this backup file on a new machine and choose to restore the System Configuration part.This will restore the certificate and private key into the ACS Certificate page.
Tnx,
somishra