Newb Questions: What are acceptable losses?

[esin]

On my first run through the game (normal). As I understand resources are limited in this game, so I'm a bit nervous about how okay it is to loose units in a battle.

Can anyone give me some perspective on the pace of the game and what an acceptable loss is that wont get me broke or slow progress to a crawl? I've been focusing on fighting weak monsters in the starting zone and yet I just came across a golem (labeled 'weak') that killed about 3/4 of my army.

And how exactly does my Hero's stats influence my army? My troops seem to have stats of their own and I don't immediately see indication of what hero stats are doing.