Changing section headings?

[Mitchell Mebane]

I'm working on cleaning up the constitution for a student organization, 
and it seems that we can never get our Word document entirely 
consistent.  So I'd like to convert it to LyX.

However, we have headings like "Article I. Purpose and Goals" and 
"Section 1. Purpose".

I'd like to use standard paragraph environments to get automatic 
numbering, but I need some way of changing, e.g., "Part I" to "Article 
I." and "1" to "Section 1.".  How would I go about doing this?  I've 
done some web searching, but to no avail...

Thanks,
Mitchell Mebane