we want to add a gas fireplace to our old brick one. Who do I call to put in a line? No clue.....
Here in central North Carolina, we could have the gas company put it in. If we buy the gas logs unit from them, they put in the gas line free (Of course, the price is buried in the price of the gas logs). But if you ask them to put in the gas line only, because you're buying the gas logs from someone else, the gas company charged an astronomical price. I forgot what it was, but it was out of the question.
Some gas logs installers will put in the gas line for you, if they have a license that allows them to do that. But there are plumbers who have taken the necessary extra training (and certification, maybe) to work on gas lines. And their prices are generally more reasonable than the gas company.
You need to ask around. In your particular location, the situation may differ from ours.
Incidentally, if you're planning to put gas into your fireplace, you should seriously consider a Direct Vent system, which is highly energy efficient and does not adversely affect indoor air quality. You might also qualify for a generous TAX CREDIT, I think up to $1500, depending on what you buy. Vendors of these units know all about the tax credit, and can tell you about it in detail.