Chuck, you should have clear tape in the kit, that's used for that purpose. Clear tape from the tail of the antenna, up to the gooey blob that seals the wires under the gasket.
The foil tape you refer to, I've seen for sealing HVAC in homes. I don't know if the adhesive is water resistant, so that would be my only concern there...
This picture shows it on mine, as I was doing it. The blob's not in place yet, nor is the rest of the clear tape which covered the wires all the way down and over the little cable guide that sits in the notch.