The campaign will most likely start with token airstrikes against supposed WMD sites, but the real meat of it will be a fairly conventional, Afghanistan-style campaign to bring the North and South No-Fly zones under allied control. That's territory where Saddam's ability to project power is already highly limited by allied overflights, and has been for ten years. The people there don't like Saddam one bit.
Expect a year-long campaign, timed to climax about six months before the next Presidential election. The rate-limiting step will be establishing the civil defense infrastructure to protect against the anthrax retaliation Saddam threatened in the Daschle letter. We won't take on Saddam directly until we have some confidence on that score.
If North and South Iraq are already under allied-sponsored governments in 2004, kicking Baghdad out from under Saddam should be a trivial matter. Just go public on the anthrax, park a B52 bomber 20,000 feet over the city, and announce that any CBW retaliation will be met with nuclear annihilation. If there are any civilians or troops left in Baghdad by this stage of the war, they will be flushed within a few hours of this announcement. Saddam, a king without a kindom, will surrender soon after. Game over.