It's never time to panic. Either the team will win the divison/pennant/WS, or they won't, and panic won't do anything to effect that. That said, concern would be appropriate right now.
Despite losing some bats in their lineup, the Yankees are playing good ball right now. Their hitting has been timely, their bullpen has kept them in games, and their rotation is pitching really well. While that has been happening, our LOB problems from earlier this year have returned. Our #2 is getting hammered every time out, and the back end of the rotation has taxed the BP pretty hard. These things go in cycles, but if this current situation were to last a couple of weeks, they could find themselves in a 5-6 game hole going into the stretch run.
I think the FO is, right or wrong, waiting for more information on Wells and Clement before making a move. It's unlikely that either of them come back and return to #3 starter form, but if they could eat some innings at the back of the rotation while keeping the team in the game, then that will help. If that is the case, I like their chances to make the playoffs, but I don't like their chances in the playoffs. The current rotation won't be strong enough to win the WS this year without a big boost (Smoltz, Schmidt, etc.).
Saving part of the future at the expense of right now could be a big mistake. Manny is having another carbon copy year, but he's approaching his mid-30's. How long will he be able to keep it up without significant injury time? Then again, trading some blue-chip prospects away for a one-year rental to go for the big prize could be a big mistake too. It's possible that whoever they acquire doesn't adjust well to the league/situation and they don't win it all. Personally, for a team with the resources to replace who they trade away, I think it is worth the shot. The Manny/Ortiz duo is a once a decade type situation. They should take advantage of it while it lasts.