Great, its not often you can say its good news when someone finds a crack in their frame. :-).
You would have had a lifetime full repalacement warranty on the frame when you got the bike though, I would be hoping for a complete free replacement. The last (free) warranty replacement I had was an 06 (I think) Mount Vision frame, which had started life as a ’97 (I think) frame. The reduced price on new frameset should only apply to the warranty on new bikes.