So there is nothing much to RPC-XML really. All it is really is sending a string of text out to a web server and getting a string back. The trick to it all is having the correct formating for the string. Had this all been more apparent to me, I would have saved a lot of time poking around.
The basic format is to pass the name of the Method you are calling and then pass the parameters for the Method. This is all encoded in XML. You can have String, Ints, Structs composed of both of these… and some other formats. You can even send binary files as a parameters. Haven’t tried that yet.
Any, it all seems pretty easy. I recommend checking out the MSDN site I referenced and giving it a try.