I'm coming from California, and would like suggestions as to what airport to fly in and out of, and how to get from and to that airport at the beginning and end of the ride.
To elaborate upon Allan's comments, use the Days Inn's shuttle from RDU terminal to the hotel (it's not very far, maybe 2 miles at most), CNC has a van that picks people up at the Days Inn and shuttles you to REI where the big buses are. You need to sign up for the appropriate shuttle van and bus as Allan noted. The reverse happens on the way back - big buses to REI, then vans to the hotel. I don't think you have any other option from CA but I would recommend coming in the night before - that's why they go to so much trouble with arranging hotel rates and vans.
Note: you do not need to stay at the Days Inn. I have stayed elsewhere and used their airport shuttle to take me to the terminal and then taken the Days Inn shuttle from the terminal to the hotel. This method does take some time but if for some reason you want/need to stay elsewhere, it's doable without too much trouble.