Good call, IMHO. He knows how Torre likes to manage, and played with a handful of the guys on the field in the championship years. This should be a good fit. And he'll be catching instructor too, and as Posada could tell you, he makes a pretty solid mentor.
But Stottlemyre? I'm not sure, given how unhappy he's been in the past couple years. Still, probably a better call than Neil Allen, and it's not as though they could get Guidry to leave the bayou.
Unless the Yankees have another deal planned (and since there is a joint meeting between the Tampa Family and New York Family of the Steinbrenner Mafia, its likely), then this move weakens the Yankees offensively and defensively.