It isn't the same thing. The goal in Iraq is to topple and rebuild a government and it was mistakenly attempted with inadequate post topple planning.
The goal in Iran would be to destroy an asset, not topple the government. We don't want to replace the Iranian government (we wouldn't mind seeing it changed).
As for the story that the White House won't rule out the nuke option, I would ask this: when has the White House (of any president) explicitly ruled out using nuclear weapons? This story comes up every once in a while. "Ohmygawd!!!!!1 The president won't rule out nukes in situation X! What a homicidal maniac he must be."
The president asks for plans on how we might go about destroying Iran's nuclear facilities. If the reports of how they are hardened are accurate, the only way it could be done simply with bombs is nuclear. To say so is not to say that will happen. Frank Kaplan at Slate (a rabid anti-Bush man) is reasonable on
his evaluation of this story.
By the way, just to get this out of the way now in case it does happen. I do not support military action to prevent Iran from developing a nuclear bomb. I believe that development of nuclear weapons (as well as chemical and biological and mechanical) is a right of a sovereign nation regardless of U.N. treaties otherwise. The only difference with Iraq is that they had signed away their rights to do so when they invaded another sovereign country and, particularly, when they lost the ensuing war.
So if it happens, I will not support it (or the troops who do it).