Regarding packs, I've found little need to access them on the slopes. What I do want in accessible (which may mean in a locker at the base of the lift, if available) are:
1. Spare gloves, for when your first pair wets out.
2. A warm fleece balaclava or buff (one I wear, the other in the pack).
3. (optional) An additional insulating layer.
4. (more optional) A pair of shoes to change into at the end of the day.
If the resort is well-equipped with hot chocolate and Liège waffles, little else is needed.
Looking at the weather in the 25F-45F range and expecting falls, I'd agree with using waterproofs. On your legs, an R1-type bottom is probably as warm as you'd want to go. Cap3 might be a better weight. For the top, a thin baselayer and an R2 would probably work.
The only reason to significantly bundle would be a large temperature drop or heavy winds. Between that and the durability issue, save the down garments for when you're done skiing. Boot fit is important; for control you'll want them nice and tight, yet too tight and you risk cold feet (insufficient blood flow). I agree with the recommendation for thinner ski socks, but you are somewhat at the mercy of the rental inventory.
Finally, see if you can book an instructor for at least a few days of the week, if not the entire week. It should be well-worth the cost, especially if you can split it with others. If you won't have more than a couple hours of instruction, I'll recommend the reading I did when teaching myself to ski.