Ford Repair: burning oil, ford crown vic, oil consumption

Question
I have a 93 ford crown vic with a 4.6 liter engine.  It's burning oil from the exhaust.  It emits a light grey smoke when idleing mostly.  Someone said I have to replace the rings.

How costly is this procedure and how long does it last usually.  

The engine has 146000 miles on it.

Thanks

Answer
Rich-

  Rings could be the problem, but 4.6L motors are usually built extremely tight and oil consumption isn't common.  My money would be more likely on bad valve seals.  The only way to know for sure would be to have the engine compression tested.  It's a simple job and it will let you know how well your rings are sealing.  Hope this helps.

Steve