the best way to tell if your Steyr has the upgraded trigger is to look at the side of trigger. There is a pin in it that appears to guide the trigger safety.
On the original triggers this pin was about a quarter of the distance from the bottom of the trigger to the top of the trigger. On the upgraded trigger it's about halfway up the trigger.
here's a picture of the early trigger
and here is the upgraded trigger
As for night sights, I think Novak makes 'em (although they don't list the Steyr on their site) http://www.novaksights.com/