Change Primary email and autodiscover records dns

Hi ,

We have two email domain on our exchange server domainA and domainB.

Currently certificate shows only domainb and dns records for splitbrain dns and autodiscover records point to autodiscover.domainB.com.

I would like to change people's primary email domain to domainA, add domainA to the certifcate and change the autodiscvoer records and created dns for autodiscover.domainB.com.

What do I have to do in order to minimize downtime and allow name resolution and autodiscover to work off of domainB?

This is Exchange 2013 Standard.

Thanks,