Hello Simon!
This process will not take more than 1 hour, usually minutes.
Its not practical to load the patch in all 15 pollers, just start on the poller where you will do the discovery of the new Devices, Test, then if for the only one that you updated to the D19 patch gets all you need from the Device, then just update others if you will need to discover those new certified Devices, because its just a Certification kit.
About the last question, in the Read said to you to stop the ehealth ( NOT the Oracle DB), apply and manually start it.
If your questions is already answered, could you please mark here as question answered please.
Kind Regards,
Alex Yasuda
CA Technologies
Sr Support Engineer