I'll just let you know straight up, you may be dissapointed by what you hear about the Y-50.
The particular suspension design the Y-50 has has been outdated for several years. Most mountain bikers didn't like it because of the pedal induced bobbing, most noticeable on climbs. I'm not sure about the carbon fiber part. I know that for awhile carbon fiber didn't live up to it's "lighter, stronger" name.
However, looking at the picture on ebay, it appears the previous owner took good care of it, and it is equipped with good parts.