Stylesheet problems (xml declaration and parameters)

I am having 2 problems in generating some XML output based on a stylesheet.

1. When I use oraxsl, the generated output does include the first 2 XML-related lines from my stylesheet definition (i.e., <? xml...> and <!DOCTYPE...>). However, when I actually process the XML from my PLSQL procedure, the output starts on the next line of my stylesheet (i.e. my first real XML user-defined tag). Why would the first 2 lines be ignored or skipped over?? Obviously without the <? xml...> tag, the output is not considered an XML document.
2. My parameters are not working, either from oraxsl or from the PLSQL procedure. For example, the generated XML output displays $UserName, rather than replacing that with the user name that is passed in. By adding some PUT_LINEs to my code, I can see that the parameter values are being passed appropriately. But then an Oracle Java stored procedure is called and I can't see what it's doing. Any ideas what I might be doing wrong??