"It seems to me the war was sold as being short, a blitzkrieg of sorts.
Now, we hear the opposite."
Well, there was a good possiblity that the war could have been much shorter. France can take some credit for making this a longer war. They will have the blood of many Iraqis and some American/Brits on their hands.
And it is a blitzkrieg, but in a sense, the French were much smarter surrendering before any enemy forces reached Paris:)

"I thought the Iraqis would welcome their "liberators" with joy and relief?"
They will. There is no doubt about. What do you expect, Iraqis "demonstrating on the street" and being slaughtered by Iraqi miltary?

"Well, a large number of areas are resisting. They hate Saddam but they also hate being invaded."
90% of Iraq don't hate being invaded. Of the soldiers it depends. First, of the Repubic guard these guys mostly would have prefered no invasion. Then there are groups of people in Iraq which are there mainly because they hate Americans and this is opportunity to fight them (I sure hope that all these people {terrorists} would join in this war- it's a much more honorable way of dying then strapping on high explosives and murdering innocent civilians). Reg Iraqi army, seem to "vote" by surrendering whenever given the real opportunity (if they hated this invasion, they would not surrender- most of these people would fight to defend their contry if they thought the current regime was worth their life).

"They are far more nationalistic in feeling than was thought in the beginning."

No, quite the contrary.

"The longer it lasts, the higher the resentment."

Well, everyone (except Iraqi crimimals, some in the French leadership, and wackjob demonstrators) wants the war to end as quickly as possible.

"Once the war will be over, it's going to be far more difficult to get any willing cooperation from Iraqis."

Oh, I think you are going to find this quite wrong- "it's going to rock your world".