Is it even possible to reset a single stage of a quest (as opposed to the entire quest)? Thing is, I've already gone in guns ablazin' and killed everybody (wanted to sneak in and save the hostages, but they started shooting at me, or maybe at Boone, in any case they're all dead), so now the Khans hate me. Which, if I'm not mistaken, means I won't be able to do some of the Great Khan side-quests, right? And being able to do the side quests when they come up is the problem I'm trying to resolve. So my questions are:

Am I mistaken and will I be able to do the side quests even though they hate me? If so, I can simply go on from where I am.

Does an opportunity to raise my rep with the Khans come up in the future (besides cheating it up with the console)? If so, ditto.

Can I reset the quest in order to negotiate rather than sneak? If so, how? I've tried to 60 (the Boulder City stage), couldn't talk to NCR guy to get the negotiate/sneak choice, tried to 50 (the previous stage, whatever that is), still couldn't talk to NCR guy. Tried with the quest stage (since I don't want to reset the entire quest), console won't accept it (didn't think it would, but tried anyway).

Or am I simply screwed and have to live with not being able to do the side quests?

And no, I (stupidly) don't have a save from which I can reload, otherwise I wouldn't be asking.

Thanks for any help.

you can still do quests for the khans. i have killed the khans at boulder city. but when i found their base, they didn't attack me. the only khans i killed were at boulder city.