tomharrison, I don't have your board and didn't have to install the EC FW tool, but I helped others successfully to walk through it. One of the gurus on this site told me the tool figures out if it is needed and then installs itself. It's not needed on your system until you get your 3700x.
If I was doing this. I would hold off until the installation of the 3700x, then install the tool, and then upgrade the BIOS.
Someone else may have a different opinion.