Problem is solved. I went through too many steps with Dell to document here so I will focus on the salient points.          Installation Failed with return code : 1642        Upgradation of SupportAssist failed.        SupportAssist download/installation failed with return code: SupportAssistUpgradeFailed         Application Exit Code: 19 In conclusion my Dell Update is working again. So is SupportAssist. I will keep Dell Update running (driver update process is fabulous) but stop the SupportAssist service as it is taking over 650 Mb of memory at the moment. But it is there if I ever need it again. Dell, please fix SupportAssist to not use so much memory! I would like to recognize Akshatha and Dilip for their valuable assistance.
Today, I uninstalled my Dell SupportAssist because it would not finish checking "Get Drivers & Downloads."  It got stuck at 80% completion.  Unfortunately, now I'm not able to install the SupportAssist download (Version 3.3.3) on my Dell XPS 15 9530 laptop with Windows 10 Pro Version 1903.  Any help in solving this problem will be greatly appreciated.  Thank you
Dell SupportAssist version 3.3.3 will not install