I’m using 6.1. I think the same thing works in earlier versions, except the locations of the services may be in different folders within the SAP adapter folder. I use these services to convert SAP IDocs from a flat file to a document and to a flat file from a document. I got some of the info from WmUsers and the rest from support. This works for my implementations. All my IDoc document structions in webmethods are defined with the E1 prefix, not E2.
IDoc Flat File to Document Structure:
pub.sap.idoc:decodeSDATA (this step converts the E2 to E1 if it isn’t already E1)
Document Structure to IDoc Flat File:
Hope this helps,