I am currently trying to create a win32 service using pywin32. My main point of reference has been this tutorial:
http://code.activestate.com/recipes/551780/
I've never used these APIs, but digging through the code, it looks like the class passed in is used to register the name of the class in the registry, so you can't do any initialization of your own. But there's a method called GetServiceCustomOption that may help:
http://mail.python.org/pipermail/python-win32/2006-April/004518.html