I just got the 2E game today. I wanted to clear up something. According to the Heroic Feat rules, a heroic feat can only be done "once per encounter". Am I right to consider an encounter to be defined as a run thru a single dungeon? I just want make sure I understand it right.

You got it right.

An encounter is one of the (usually two) parts of a quest.

On p.18 among steps between encounters, it is said that a hero player "flips his Hero sheet face up".

Thanks. Good to know I had it right.

And remember that en encounter is just 1/2 of a quest.

Also: A problem we had during the first rans we did: In the quest guide, when you check for what monsters to use each encounter- remember that the symbols are meant to be for each side/encounter. For example: If you can use Shadow Dragons in the first encounter, you might not be able to use them in the second, if the symbols dont match!