I'd like some lights in street lamps in my worldspace to appear at night only. Is there maybe a script or something I can use to make the lights appear at say, 6PM-ish, and disappear at 6AM again?

Use GetGameHour and Enable/Disable.

I don't script, and this is only something I chanced upon ages ago but it might push you in some direction:

http://geck.gamesas.com/index.php/Reference#Emittance

The bit about the Megaton lights.