"Once we've dealt Saddam's forces an initial, devastating blow, there's a good chance that part of the Iraqi military, as well as Northen Kurds and Southern Shiites, will rise up in revolt against him, as they did in 1991.

Should we:

1) continue full speed ahead onto Baghdad to take out Saddam?

2) step back and let the Iraqis finish the job themselves, providing them with air support (which we failed to do in 1991)?"

Not sure how you deliver this devastating blow.
But I'm against the idea of "let the Iraqis finish the job themselves".
Without any particular intelligence, I would guess the best way of dealing with Saddam is to take his country first then worry about the cities. The best thing the Iraqis can do is get away from Saddam's forces. If Saddam brings out his army; we will flatten it. We control the air and the night this makes any offensive action difficult. So we cut off the major cities and control towns and large areas of the land. If we still have resistance, we take the cities, block by block.
Now, Saddam's forces are facing an unwinable war with a leader who is a fool. The miltary forces follow a chain of command, unless there are consequences, any leader does not need to follow a order, so Saddam is going to have a serious control problem. If groups of Saddam's forces separate and switch sides- unless it's very early in the conflict, they should in most circumstances be considered prisoners of war (don't have them fighting).