when i moved both my 55's, i kept the gravel in and a bit of water (enough to cover the gravel). even had some green shrimp survive the ride in the back of an open truck in really cool weather!
as for the algae, just scrub it off with a sponge or a piece of polyester batting (i find this works wonderfully for my glass tanks, and i use the batting as polishing media in my filters too). be very careful and gentle while scrubbing the edge of the silicone, you don't want to lift the edge of it at all.
i would highly suggest doing a fill/leak test in your garage before moving the tank inside. fill 'er up and leave it for a couple days to ensure there are no issues with the seams.
if you are at all concerned about any nasties in the tank, let it soak with a bit of bleach in the water, then rinse rinse rinse, set it out in the sun for a day, and then fill it again and use a hefty dose of Prime dechlorinator. this will neutralize any residual bleach.