im stuck on the mission they went that a way, i killed the great kahns in boulder city, looted jessups body and all i got was jessups bandana, get playin and figured out i had messed up, so dnow i cant intercept ythe great kahns there, people on here told me to go to red rock canyon and do oh my papa mission and it would fix everything and let me continue

just kill them all and see what happens to ur mission

Look in your pipboy, under the Misc Quest Notes there should be a note entitled "Chairman Job Offer". Read this and They Went Thataway concludes.

This note should have been on Jessup's corpse . . . you probably already have it. If you check and for some reason you don't . . . then head back to where you killed him and look around.

well i dont have the note and his body is gone guess im startin over or just sellin it

Or you can just head to Vegas.

Starting over is not a bad idea because you were not that far into the game, just don't kill Jessup next time.

You don't need the note or the quest update, technically. You've been told that Bennie was heading back to the Strip, so head to the Strip and things should proceed normally from there.

Most quests in NV have a potential to get screwed up, as a vast majority use the same key areas and plots.
Just given a spin depending on which faction or group you are working with.
It does not break the game often or in any serious way, my first play through I ended up winding up every major group and killing just about all named NPC's in them, and still finished the game.

Just play through, as you will find the game starts to have at least three ways to progress as soon as you hit the NV strip.

Hmm . . . I killed Jessup. Can't remember if the note was on his body or not, but I found it somewhere. If you head to Vegas, your Quest will update when you meet certain key characters. No big deal and you don't really miss anything.