vamsi -
based on what i saw yesterday afternoon (please see my Trip Report in that forum).... the switchbacks will be "doable" when you want to climb. you may want an ice axe and crampons/microspikes (and know how to use them) with you just in case.
in terms of training, IMHO long multi-hour hikes are key.... ideally a couple of training hikes of 5+ hours. it sounds like you have a few of those planned and at some altitude. take good notes on what you eat/drink and how your body reacts to Mt. Dana. that will be key to figuring out your plan for Whitney.
