Re: SLR LENS for Antartica 2009!
My 100mm is a macro lens too and only f3.5, it's bright in the Antarctic summer and most lenses are at their best quality from about f5.6 to 11, don't worry about silly-expensive fast lenses. It sounds like you already have the lenses you need. I'm assuming that they are of at least reasonable quality? Budget lenses are not worth the savings like any budget tool.
Fixed length lenses are always going to be better and faster than a zoom in the same region for the same price, and better quality too. I prefer to use my feet to move and frame the picture, not the zoom. You'll probably get a gaggle of people with their cameras standing around a penguin colony or near some seals who are upright and hardly walk anywhere, they will also probably have the most expensive stuff (all the gear - no idea).
To take the best pics, you need to be moving around, thinking of background, thinking of your level and prespective. There's little better a picture can be with more expensive equipment. "Professional" standard equipment will give high quality results, but much of what you buy is in terms of facilities and interchangeablity (that the vast majority of people will never use) and reliability and ruggedness (at the expense of weight and size as well as cost).
As for memory, I'd say you need to take enough to take 100 shots a day at maximum resolution (this may well be significant overkill, more reason to practise before you go). You may also want to take short movies on your slr if you don't have a separate movie camera, so you'll need to work out what that comes to. Some tour ships have the facility for you to burn your memory card to disc on board if your card gets full, so it may be worth asking this question?
If you don't normally take many pictures, I'd spend time before you go practising as much as you can to get better. Only by taking pictures and looking at the results will you improve, better that happens at home than in the limited time you have in Antarctica.