This HK is actually not that expensive. You can find them for around 500$ USD if you look around. I don't own one, but shot a friends overseas, and it's a HELL of a lot of fun, and cheap. I love .22's.
As for the sighting system, you won't find better iron sights out to 50 or 75 yards than the HK sights.
http://en.wikipedia.org/wiki/File:Visierlinie.jpgThis is the general idea, and it's your typical graduated sight, just turn and burn.
I'm actually getting jealous/angry, as this is one of the FEW new firearms that our RCMP overseers here in Canada aren't allowing into the country for some crazy reason, as pretty much everything else, even 7" AR15s are coming in. I hope you get it Wab.