Had to replace the hard drive on 20" imac. There was a SMART failure.
The repair was unlike any repair before. In replacing the drive I hit two troublespots both having to do with over-spinning the replacement drive. The first part had to do with reversing the way a connecting cable was placed in the drive. The second had to do with buying the exact brand hard drive that the iMac was originally installed with. Through trial and error, I ended up cracking open the imac about 3 different times before things ended up well. That wasn't so pleasant but got the job done.
While documentation for these problems were ultimately there - the documentation could be better. I ended up buying two hard drives to solve the problem and it's not clear to me whether this is a problem with ALL imac or only this particular mac. :(