Forum:Dialogue Reset?

Is there any conceiveable way to reset dialogue trees with certain characters in Fallout 2? I've really effed up some stuff-- Dr. Troy in Vault City seemed way too shady so I told him I wouldn't deliver the Jet sample to him, now he won't make the antidote! Also, I never got the ghost farm quest in Modoc, so I'm gonna get a really crappy ending if I don't find a way to reset my associations with these guys! Any help?