If you are coming out for a week or more, you probably want to buy a season pass. The Epic Pass gets you all of the resorts in the area minus Copper and Loveland.
I'd find out if you are crashing with your buds or not. VRBO tends to be a good spot to find lodging. Alpine Inn has some of the cheapest rates in Summit county.
Airfare, if available fly Southwest. They do not charge for board bags or bags in general. When other airlines offer cheaper flights than Southwest, they typically more than make up for it with baggage charges. Not too mention they don't often beat SW's prices anyway.