I was fortunate enough to go to Torres del Paine in January last year. Let me say you have made an excellent choice - it is one of the most amazing places I have ever experienced!
I spent only 5 days in the national park because of a (self-imposed) tight schedule, but that was enough time for me to hike the 'W' route. This is one of the two main trekking routes in the park, the other being the slightly longer Paine circuit (7-8 days). The W route is shaped like the letter W (duh!) and allows you to see all the highlights of the park including Glacier Grey, Paine Grande, the Valle Frances, Cuernos del Paine and of course the Torres. On the Paine circuit you also climb over a pass (the name escapes me) with high level views over Glacier Grey and trek through some of the remoter areas of the park, but it doesn't include Valle Frances.
The park is easily reached from Puerto Natales, take a map though because the trails aren't signposted. I took my tent and all my provisions - there are some very basic campgrounds and you can also camp outside most of the refuges. These sites can get very crowded in high season. I had limited experience of the refuges but they all seemed very clean and well equipped, although pricey (I seem to remember a can of Coke costing me about £3!) The refuges have a very international flavour because of the diversity of people there.
In 5 days I experienced 4 seasons of weather - that is pretty much guaranteed even in summer! I was warm enough with base layer, thick fleece and waterproof (I wore my waterproof most of the time because of the incessant strong winds!) However there were some very warm, dry sunny days thrown in too.
I have so many fond memories of Torres del Paine: glistening turquoise lakes, shadows on the glaciers as the clouds danced across the mountains, watching guanaco and condors circling around the Cuernos, my early morning climb to the base of the Torres in perfect weather... I could go on and on, and probably already have!
