2000 Altima When at idle, I smell burning oil.

The car idles lower than it used to, almost stalls. There is oil on the driveway, more towards the passenger side of the car. On the passenger side back rim, as well as the bumper around the muffler their is black, but I do not see smoke when the car is running. When I first start the car, there is a squeal like a belt is loose, but a little different. It stops after 15 seconds. It squeals everytime I start the car, whether the engine is warm or cold. While I am driving, if I accelerate and the RMPs go over 5000, I hear the valves rattle. Is this a major repair?