As Eric mentioned, a heading can be created by simply typing, so making that detect whether a new heading is created is possible, but I guess it would require some ugly hacks. Maybe if you could hook into the font-lock code, but like I said...ugly hacks. :)
However, it would be easy to add advice to the heading-creating commands, so if you always use those to create headings, that would do it for you. For modification time, that would be more challenging. I guess you could use post-command-hook and update an mtime property in the current node with every keystroke. Another way might be to add a function to the before-save-hook that would diff the buffer with the file and update the mtime in each node that has been changed.
