Okay, I got a little help from @mflatt and this is probably what you want.
#lang scribble/base
@(require (only-in scribble/core make-style)
(only-in scribble/latex-properties latex-defaults+replacements))
@(define my-style
(make-style
#f
(list (latex-defaults+replacements
(list 'collects #"scribble" #"scribble-prefix.tex")
(list 'collects #"scribble" #"scribble-style.tex")
'()
(hash "scribble-load-replace.tex" #"\\renewcommand{\\packageMathabx}{\\relax}\n")))))
@title[#:style my-style]{Discourse}
@author{Racket}
(dialogue)