I hope you enjoy your trip to Antarctica, I'm sure it'll be a fabulous trip. As for clothing, it will cold but not really cold. As your trip will be in the Antarctic summer, you won't need to take any real extreme cold weather gear. Temperatures on many or most days will hover around freezing point, maybe dropping to an extreme of -10?C (20F). Obviously people adapt to the cold in different ways and I've seen some tourists in the Antarctic in light-weight clothing while others are wrapped up like the Michelin man in the same conditions. Layering is the key, then you can be flexible according to conditions.
There's a few pages you may find useful, not sure if you've seen them yet:
Clothing (scroll down a bit)
If you're going in January, I would get a camera as soon as possible and practise using it as much as you can before you go, rather than learning when you need to be able to take those never to be repeated shots. Digital cameras are fine for the Antarctic summer, make sure you take at least one spare rechargeable battery set (preferably two) to carry with you as they don't last as long in the cold.
Cameras that "work best" are fully mechanical manual 35mm ones, but they are few and far between these days and are at the high end of the pricing scale. I used to let mine just adjust to the ambient temperature and never had any problems down to -30C with it other than the light meter packing up - it's highly unlikely you'll meet such conditions though.