I'm figuring that it is either those or the valve seals. I got the smoke on idle and start-up, but also I get what appears to be some kind of black material that comes out of the exhaust pipes, I'm guessing oil. And the engine seems to be going through oil a lot. The engine has 124,xxx miles on it.

 

Most probably valve seals. You can replace them for less than $50 and do it with the heads on the engine.

 

why don't you try a compression and/or leak down test and then you'd know what you had and not be guessing or replacing parts that didn't need to be replaced