1993 Jeep Cherokee Burning Oil

I recently had the transmission replaced. Now it is emitting black smoke from the exhaust pipes. I had an oil change and when the engine is just warming up or the weather is cool, the smoke does not appear. However, after the jeep has been running for a time, or if I am sitting still in hot weather then heavy smoke emits. I save space between me an other vehicles so that I can roll forward a few inches - that slows down the smoking during the movement, but it immediately returns when I come to a complete stop while the motor is running. A friend, who is not a mechanic, said I might need to get the "Rings" replaced, and that, since I am having that done, I may as well get the "Heads" replaced as well. This will cost close to $2,000. My question is, are those repairs possibly what could correct the smoking in hot weather or when the engine is hot?