Welcome to the boards honey. This is a great site, very motivational and helpful. We have a lot in common, I'm also in my 40's, started with 124 pounds to lose, and I ski! Although admittedly skiing isn't really my thing, but the DH would rather ski than breathe, and for some crazy reason the children all got that genetic defect too...
Do you know how many calories/hour skiing burns? It's an insane workout, and waaaayyyy more fun than a treadmill, so you might want to rethink that snowpants thing. Buy them second hand, heck I have a pair I'll send you, but don't stay off the slopes because of some mental road block over a clothing size. Also another thing you might think about is that right now you have more insulation than you need, at my heaviest I wore my snowpants to the slope and spent the entire day sweating in them. Maybe you can find a pair of wind breakers to wear over some layers, long johns, sweat pants etc? Swallow your pride, put on some fat ski pants and get your fanny to the mountain. Okay?
As for a place to start, one of my best buds is a nutritionist, and she gave me the best advice. She encouraged me to write down what I was eating for 3 days, not to diet, just to record. After that exercise, it was very clear exactly where my habits needed improvement.
Starting weight: 244.6 lbs. 10/01/09
Pounds lost: 80.6 lbs
Current weight: 164 lbs
Goal weight: 120 lbs
Weight to go: 44 lbs
Goal Date: 1/1/13