For the error you're experiencing, contact McAfee support so they can give you a patch for your specific problem. to either download the installers or packages (for example VSE 8.7), you need to have a "grant number". such number will give you access both to downloads and support. you have to ask who bought the Suite of the products youre running, such person must have received the Proof of entitlement, which has the grant number.
as for what you want to do to go to version 8.7, you have to create a task for uninstallation of VSE, and a task for installation of VSE 8.7 AFTER importing VSE 8.7 package into the master repository. once thats done, you run the desinstallation task on the 8.8 machines, and when you got them ready, run the 8.7 installation task.
Hope it helps,
Thanks for the infor Chares. When Patch 4 finally came out t automatically populated in the ePo over which I Admin & I was able to easily set to push!