You may check the site on SAP Service Marketplace featuring the rapid-deployment solutions for SAP MDG. It includes info on data remediation using SAP MDG integration with SAP Information Steward. See the RDS for SAP MDG site.
In addition, on the SAP MDG site on SCN, there's also a youtube video showing such remediation process, and there's an SCN blog by Steffen Ulmer about data remediation based on MDG and Information Steward.
Hope this helps,
Markus