The HAL PDF describing the program is pretty helpful. It's on the Club Orange page of the HAL website. As far as cost - this is what it says:
"$25/person/day on cruises up to 13 days $15/person/day on cruises 13+ days."
After reading these threads recently I looked into CO and decided to see if it was available on my February cruise. It actually was. And though it did not appear as though there were any cabins were available for the upgrade - I was wondering what the "alterative benefit" would be - they found me one. I went from a VH balcony - which I was perfectly happy with - to a VA. Since I was on a roll I also booked it for my August cruise on the NS. A separate dining room will be lovely. Again, I went from a VH to a VA. My TA did take some educating and she finally found someone at HAL who understood the program.