I’m currently subscribed to the vip Patreon package. If I buy the one time payment here, $39 will I have to re-install everything again on my computer? Will I lose everything that I have already saved, scenes, looks and etc. Or is it possible just to update the key and good to go?

You would need to install this, then after installation copy over your AddonPackages, Custom, and Saves folders from your old Virt-a-Mate installation to the new VaMX installation.