Can I add a second table (high-level) of contents and show only H1 headings? When I tried to add a second TOC, it seemed to just scroll down to the bottom of my existing TOC.
Yes, that is possible. I just tested it in MS Word 2003 by creating different H1, H2 and H3 headings. On the first page I inserted the complete TOC, under (or onto the second page with a page break [Ctrl-Enter]) I inserted another TOC including only H1 headings, and this works correctly.
Please give it a try in another document.