Hi Nate
I tried in v9 and editing of questions and answer wording was possible even when an attempt had been made on the question.
As long as you don't change the option that is the right answer the grades will be correct (so if choice 1 is the correct answer you can change wording of choice 1 but not the weighting)
If you look at the quiz attempt responses the original answer when the quiz was submitted is saved as the response but new wording is shown in the quiz question when re attempting.
regards