By little flat ring, I assume you mean the tensioner pulley. And yes, that is supposed to turn. It is also a first suspect for your problem. You should be able to get a replacement at your local autoparts store or, failing that, at your local GM dealer.
You can replace it without removing the tensioner.
Edit: Here'* a pic of my bad tensioner (idler) pulley:
Notice how my bearings froze and the pulley literally meted off the old bearing races. All the bearings were gone.
And here'* the new one
Mike: 1997 SE w/ 183K, aka White Horse
, Gutted Airbox w/K&N, drilled 180* t-stat, tint all around, clear corners w/SilverStars, "PONTIAC" light up tail, PEMs, NGK TR55s