If your documents are in SharePoint, you can use the relink feature to fix up a bunch of documents at once.
If not, I don't believe InfoPath provides an easy way to do this (besides the manual text editor approach). That's why we created the Modify PI tool, which can change the HREF for an entire folder full of XMLs at once. How about giving it a try?
http://www.qdabra.com/en/products/QdModifyPITool.aspx