Re: SLR LENS for Antartica 2009!
I took a 28mm, a 50mm, a 70-200 zoom and a 2x teleconverter with me to Antarctica. When I could (after a year!) I bought a fixed 100mm lens which pretty much became my standard lens for wildlife (and most other things too in fact).
Of the pictures on this site that are mine, they are about 50% with 100mm, 30% with 50mm, 15% with the zoom and 5% or less with the 28mm. I used the teleconverter a handful of times only and took only very few decent pictures with it.
I am a great believer that the best accessory you can get for your slr is the ability and willingness to walk around and find the best postion. The 100mm wasn't really necessary for wildlife pics, I like the perspective it gives and it allowed me to stay a little further away from my subject.
I liked the way I could carry the 100mm on my camera in a waist-belt case with the 50mm lens at the bottom of the case. Everything else was in my rucsac.
Wide angles are a matter of style rather than necessity and I'm not that keen on them, personally I wouldn't even bother with a 28mm, I'd get a 35mm instead maybe as one end of a zoom.
500mm? I see no reason for this whatsoever. You might be able to get some pictures of seals on distant ice-floes and I'm sure that someone will say they got some great picture with their 500mm lens. A couple of guys I was in Antarctica with who became professional photographers owned long lenses, but virtually never used them. As we spent 2 years, we had the luxury of spotting potential pictures in advance and planning for them, this is when the longer lenses would be used and usually for the perspective they gave rather than "reaching" the subject.
As your time is limited, I'd suggest 35, 50, 100, 200 and spend your time thinking about how to use what is attached to your camera at the time and taking lots of pictures. Get loads of memory and/or the ability to download to laptop. Record everything at maximum resolution. Get a tripod and a bean bag or similar to staedy the camera (I used to use the top of my rucsac propped against a rock).
I used to aim to take pictures at f5.6-11 only with as fast a shutter speed as possible for the best quality. I'd also recommend as much photography practise before you go as possible so you're as good as you can be when you get there.
I haven't been to Livingstone Island, if there are fur seals, you will be able to see them, for many people fur seals get too close for comfort! They are my favourite Antarctic animal though, your 70-200 will easily be adequate.