Did you know that it is legal for Americans to visit Iran as a tourist, and that the country is peaceful and they like Americans there? You can find tourist information at:
http://www.irpedia.com/
In the Iran - Iraq war in the 1980's, we sided with Iraq, and gave weapons to our former ally, Saddam Hussein. - As a result, half a million Iranians were killed. It is amazing that they still like us.
See: http://en.wikipedia.org/wiki/U.S._support_for_Iraq_during_the_Iran-Iraq_war
So far, we have invaded two of Iran's neighbors, Iraq and Afghanistan. We don't invade countries that have Nukes- even Islamic countries such as Pakistan or India (which has a large Islamic population.) - It should be no surprise if it turns out that there are a few people in Iran who would feel safer if they had one.
Regarding the statements of Iran's president, Mahmoud Ahmadinejad, first of all he is a little wacky and he is not really in control of the country. The mullahs are. Second, he hasn't threatened to attack Israel. He did say that he believed Israel should cease to exist - but he proposed that everybody in the area which the Arabs call Palestine should be able to vote on the future of the region. - Since Arabs populations are growing more rapidly than the Jewish population, if Israel allowed such a "One state" solution, Israel eventually could be voted out existence. Third, some of the things he has said, may be part of a strategy to keep oil prices high. - If people worry that the supply will be interrupted, they will pay more. Fourth, most Iranians don't want to commit suicide - They know Israel has nukes. They would be crazy to start a war.
See: http://en.wikipedia.org/wiki/Mahmoud_Ahmadinejad
But to answer your question specifically, I don't think there is a good reason to go to war with Iran, regardless of what it might do to the price of gas - but you are right --a war would badly interrupt supplies.