Chad,
I think your issue is that you may be using the incorrect url.. or may need to consider a relative path to your xsjs service.
also, I noticed you are posting an object but in your url you are also passing a query string... you should be able to get the json string as you have in your code.. if you need to conver to a json object.. then do
var body = JSON.parse($.request.body.asString());