How to tell which are bonus missions?

[lokiju]

Hello. I just started the game and have 1 questions:

1) How do you tell if a mission is a main story or bonus one? Some have gold stars, others don't.

2) In the 2nd mission, you choose thieves or undead...I chose undead. Does it really matter (are there different artifacts, etc?)? Once you make that choice, the other is lost forever?

This seems too confusing/overwhelming compared to Fantasy Wars. I am a completest, and hate to miss things.