Would Ned have actually taken the Black?

[WSmith84]

Well, there's the complication of Jaime being Robb's hostage; Robb may have demanded that Ned be free from any oath to the Wall as part of the trade deal.

Sadly, I don't think it mattered. Ned's medical condition appeared extremely poor; I think he was on his way out regardless.

[Nevets]

Ned would absolutely take the Black.  He would take an oath to do so, and the reason for that oath would be Sansa's safety.  Ned is, if nothing else, a man of his word.  He keeps it even when it becomes very difficult or inconvenient to do so.  Even Cersei believes that he would keep it, which is why she is willing to make the offer in the first place..  So, no, he would not renege and help out Robb.  Robb is on his own.

[Colonel Green]

If he actually had to go through with the deal, yes, Ned would.  He swore an oath, and the same incentive that made him confess in the first place (saving his daughter) still applies.

Now, had Ned not been executed, the deal would not have gone through.  After Jaime was routed in the field, Tywin would have brokered an exchange of Ned for Jaime as part of a cessation of hostilities.

[Lord Lannister]

37 minutes ago, Colonel Green said:

Now, had Ned not been executed, the deal would not have gone through.  After Jaime was routed in the field, Tywin would have brokered an exchange of Ned for Jaime as part of a cessation of hostilities.

Agreed on this point. Even had Cersei put him on a ship for Eastwatch that day, a raven from Tywin would've beaten him there.