Hi,
I would suggest to upgrade the SEPM & to stay on more safer side take complete backup prior to upgrade.
For clients test the AutoUpgrade process before you attempt to upgrade a large number of clients in your production network. If you do not have a test network, you can create a test group within your production network. For this test, you add a few non-critical clients to the test group and then upgrade them by using AutoUpgrade.
This way you can ensure everything is working as expected.