Units

I've always done triggers but never custom units until lately. How do you get it to say what level the creep is right under it's name?

Elaborate a bit, where do you want to see the level: in the UI panel (with all his stats) or in the field.

In the UI panel, when you select the unit.

I think I know what you're asking, and if I do, then the answer is that units controlled by Neutral Hostile will show their level under their name in-game.

Only Neutral Hostile though? Not a custom force I made?

As far as I know, it's a trait peculiar to Neutral Hostile units, and can't be duplicated.

On the other hand, if you only need it for one player, maybe you can modify Neutral Hostile's ally properties. There are other tricky bits with using Neutral players, but it can work.