I've read that carefully more than once and there is no mention of whether an uninstall is advised.
What, exactly, is not clear about this ?
Since we haven't added anything extra the "how to get it" instructions, you can safely assume there's nothing else to do other than installing the latest Full GSX installer.
I'll repeat it again: the very fact that "there is no mention of whether an uninstall is advised", should be an indication that's not required. Not that it wouldn't make any difference if you do it anyway. It simply doesn't matter.