is 42k triangles too much for a game character for PC in unity?,
I would say that 42k is fine but it depends one the platform that you are aiming at and what sort of game it is. 42k character wouldnt be good for a multiplayer game for example and mobile, but I would say that it is fine for a pc single player game. This isnt made in the Unity engine but the character Jak from Jak and daxter 2 for playstation 2 from 2003 is 10k polygons with is 20k tris.
The head on Jason from Far cry 3 is 17k polys, and the body is 30k
Yes. Try to stay around 5k-10k for an important character. Be sure to use normal maps. You can dramatically reduce polycount this way.