I have a rock gollem that I made in TrueSpace.

Once it was in MED, it came out to 7k faces.

This gollem will be an enemy in the game that the player must either fight or avoid, so my question is, is 7k too much or should it be fine?

Its an adventure/thief game, 3rd person camera.

it's ok but you may consider using some LODs.

It entirely depends on what else can be onscreen at the same time.

Having it in an open environment in the distance heading towards you with 10 of his buddies you'll definately need to get LODing sorted.

If you'll only ever see them up close with not much else happening then 7,000 won't be any problem.