I've only ever sat in the 500 level for the games i've been too, never been disappointed. The hghest I've sat is row L in section 531 (if I remember right), probably along the 10 yard line, closed end. Great view, these were actually the seats I sat in for the 2008 Afc Championship.
Enjoy the game, your first game at Heinz will be a great memory, especially when Steelers come away with a victory over the Ratbirds.
Please make sure you are in your seats near the end of the 3rd, beginning of 4th when Renegade gets played, you'll be grinning from ear to ear. This has always been the time they have played it when I have been at games, stadium will be going crazy...