Does webMethods provide any whitepapers for converting already implemented webMethods integration solutions to webServices. Mainly in terms of overall solution and architecting around it.
There is lots and lots of marketing stuff, webinars, etc. on Service-Orientation in general, but I don’t know of any webMethods docs on the topic you mentioned.
If your existing integration services are mostly implemented in Integration Server, you can find lots of information here in this (web services / soap) forum on how to expose IS services as web services.
Lately, I’ve found Thomas Erl’s SOA book to be useful with regard to implementing SOA principles.
Since the web services support in Integration Server does not yet support some componenets of the WS-I Basic Profile and WS-I Basic Security Profile, you’ll want to either build some of the capabilities like WS-Security (including encryption and signature) in IS or use other WM products such as ServiceNet or Glue to add them.