Check the tutorial for the Goldsource one.
It's the same thing.
But there's something called a
trigger transition that copies all the entities within the volume to the next map. The trigger transition references the same landmark used for the level change.
http://twhl.co.za/tutorial.php?id=62That's the level change tutorial..
In source, there's still the landmarks, there's still the trigger_changelevel, you still need one in each level with one of the same named landmarks in each level as well..
Good luck.