XSL to ODF/OOXML

I'm scouring the internet looking for leads on creating ODF/OOXML with
XSL transforms. I'm not really finding a whole lot, other than command
line programs which accomplish as much.

I have a website with lots of reports and, ideally, I'd like to have
an 'export to Word' feature. Is this just another XSL transform that
requires me learning the appropriate output schema or is there
something additional that needs to be done?

Also, I already have HTML versions of the reports I need (nothing too
complicated). I'm wondering if I can use the XHTML output as my source
XML and have one stylesheet that converts all of my documents into the
appropriate format? Or am I reaching for the philosopher's stone too
soon?