I think if the US were to invade Iran, it's almost certainly going to lead to nuclear war considering that it's common knowledge that Iran has WMD's. OK, maybe not common knowledge, but it's almost certainly true. Hence my question, do you think there'll be anything left.

I think Iran may have a nuke or two stashed away that they bought off the shelf from North Korea or A.Q. Khan...but it's far from certain. But in all honesty, I hope they do. The rest of the world has been putting up with our hypocritical crap for long enough.

No mystery about it. We intend to attack Iran. It is unlikely they have a bomb. Plans have long been ongoing for coordinated attacks on their 'well dug in' nuclear program. A least two American spy planes have been lost - maybe shot down - in Iran probably doing those searches. At least two that Iran is willing to admit to. Attempt will probably be a major and coordinated air attack on these well buried sights sometime before Iran gets uranium sufficiently enriched. IOW that air attack will probably be just under a year from now. What happens after that has just too many variables to predict.

How enriched need uranium be? Bomb on Hiroshima was only as enriched as uranium after being expended in a conventional nuclear power plant. Better bombs would be even higher grade. As I recall numbers, Iran would need something like 15,000 centrifuges to process uranium gas. It is believed they have just recently finished setting up most if not all this equipment.

No they do not yet have a bomb. And it will not be the mythical 'end of the world' scenario. What it would be is reams of US troops coming home with massive nuclear induced injuries. A problem that could have long ago been avoided had the United States not intentionally undermined the entire Iranian reform movement with all this open talk of war.

How long ago was it completely obvious to Iran that the US intended - actually intended - to attack? Not just threaten - literally make those intensions obvious.
In Jan 2005:
The real cost of IRAQ: PTSD and the second war
In Aug 2005:
Understanding terrorism
In Feb 2005:
100,000 Iraqi Civilians have died in current war
In Dec 2004: In Nov 2004: In Oct 2004:

It's been replaced by what is possibly the most awesome song in the universe. What's wrong with that?

Our troops might well sustain injuries from radiation. So might a lot of other folks in the vicinity. I haven't read enough on Iran's nuclear capacities whether real or imagined to comment on that aspect of it.

What I can state is that if the US plans on invading Iran at any time in the near future, it will be draftees coming home with injuries whether from radiation or conventional weaponary. The Army is already facing serious shortages of personnel in the war in Iraq. Morale is getting lower with every soldier's tour of duty over there. It is not uncommon for soldiers to have made three deployments to Iraq, already. Supplies of EVERYTHING are limited. Active duty soldiers see how the VA treats vets which is not well at all. The benefit package the armed services once offered career soldiers and their dependents falls far short of what was offered in the old days. New policies have the effect of keeping soldiers in the military indefinately, long after their enlistment period was supposed to have ended.

The politician who orders an invasion of Iran will also be ordering the re-instatement of the draft or be faced with the very real possibility of a forced withdrawal from the conflict due to manpower shortages. One or the other.