He says there is honey seeping out of the top of his window on the inside.
Just remember that as soon as the bees are gone, there are no bees ventilating
their old nest, and thus you could see a lot more honey as the temperature arises inside. If you consider this to be bad for the garage, it's probably better to rip up the wall and remove the comb (and use it with rubber bands as Robo says), and then seal the wall so there won't be any new bee colony there.
Haven't been into removing bees from walls, but I have seen a lot of warnings about melting honey causing a lot of damage.