Menu splitting

I have a fairly complex public navigation system, and I'd like to use one single menu for it.
However, I don't want that one menu in one block.
I'd like to put a single level at the top, and then a secondary level on the side.

For some areas, I'd like to "shift" the menu down, so that the top level links are actually the second level of the heirarchy, and the side links are the third level.

I've been looking at the menu system documentation. The function menu_primary_links() looks like a step in the right direction... but when I try to call that from a block I get the error:

Fatal error: Call to undefined function: menu_secondary_links() in /home/wwwroot/includes/common.inc(1857) : eval()'d code on line 2

Any ideas on either of those issues?

Thanks...