The belt tensioner comes with the tensioner and the pulley. It does not come with the damper, which you can check by removing the top bolt and pushing up and down to see if it damps okay. It should be reasonably stiff. If not, then I would replace it while you've got things apart. If the shock is okay, but the bushing is worn, I would just rig something to take up the slack, like a washer or teflon tape or something (you can't buy them separately).

Orientation of the tensioner/bracket is important to making sure everything fits properly. This post has some good pictures and stuff:

1993 300se belt tensioner adjustment

Does your engine overheat in stop and go traffic? If not, your fan clutch is probably okay. Good fan clutches will also make a whooshing noise when you first start the car, and then get quiet after a few seconds, and then make the whooshing noise whenever the engine is running hot.