filed for an uncontested divorce. Can I withdraw the petition to file for a contested, 'fault' divorce

i'm not sure what you mean by uncontested.  Did your Complaint say only that you wanted a divorce, and did not include anything else?  if that's it, and now you want the Court to be involved with the economic aspects of the case, or any other aspect or your case, you can amend the Complaint to include whatever else you want the court to be involved in.  i hope this helps.