"Is it the oil? Unlikely..but then, why are there threats of preventing any oil deals to countries that might oppose war?"

You are missing the point. The "countries which are opposing the war" have oil deals with Saddam. Whether these deals will be honored by the new regime is certainly debatable (these deals could very well have made by Saddam with Saddem not even intending to honor them- merely using these promises as a lever of dividing opposition).

"(Well, again, it's not that important as the dealers who do get the bargain will sell their oil everywhere there's a market."

If the risks in involved are lowered, then the will be no "bargains"- the oil will be sold at market prices. Though lowering overall risk does tend to lower the price.

"Is it the WMD? But then, why are there discussions with North Korea which does have far more dangerous WMD's than Iraq?"

North Korea is (was) a client state of China. Dealing with N Korea will involve the Chinese. I think America would happy if China were to take a more leading role in dealing with N Korea. If China doesn't see N Korea's weapon proliferation as problem that needs to be solved, America isn't going to get very far in dealing with N Korea. N Korea is "in the news" because the N Korea goverment wants to get aid from America. N Korea certainty is a problem, but it's a problem which is best solved through diplomacy- the main parties involved being S Korea, Japan, China, N Korea- and US wants to be involved to help bring bring about a resolution to this diplomacy.
In other words this N Korea thing is simply a red herring

"Is it Saddam in person? Well, he's probably liked by only 20% of his population (or only 4,400,000 persons as opposed to 6 Billion earthlings)."

No one likes Saddam- probably including his mother. Saddam is a monster. Monsters don't like people, they fear people, and want everyone to fear them.

"Ok, he must go.
But doing so by sending bombers, tanks, heavily armed troops....Thousand of Iraqis will die (a huge number being children) while Saddam will have ample time to get lost and disappear, like OBL did.
But even then, because there'd be a new Iraqi government, who will care where Saddam is?"

There is a huge difference between OBL & Saddam. No one cares if Saddam runs away- he is a mass murderer, but as far as world power he would be insignificant- he knows it and that's one reason he won't run away. OBL is a cult leader. Even if OBL dies, he still has power.
The only significance of Saddam running away is he has certainly stashed huge globs of Iraq wealth somewhere.

"And the new Iraqi government...It must first be accepted by the Iraqis.
Otherwise we'd only replace a dictator by another dictator and in 10 years time, who knows what he might think of the west?
After all, he might very well form a religious oriented country and befriend Iran."

Iran is becoming more democratic. The fact that it is a "religious oriented country" is not a particular problem. The US is a "religious oriented country". So is France. Anyone very familar with the major religions knows there is a lot of common ground amongst them.

"Not what Donald wanted back in 1984.
Wars have short term effects...but long term ones too."

What the US and UN is trying do is unite nations throughout the world. Having the Arab worlds united is what we desire.
The idea of having opposing spheres of powers is an old European concept- it not really an American one. Back in '84 we were in a Cold War with USSR, our priority was in containing USSR and we needed countries which were opposed to USSR.
The Cold War is over.