With a ventless gas fireplace, well, of course, you don't need a vent. And if it is just for appearance, no blower to heat, you don't even need electricity run to the fireplace. Assuming you have a gas service for furnace and/or water heater, the plumber can just tap in. That should be simple if you have a crawlspace or basement. If on a slab it is going to be difficult.
You say you need to have it installed, so if you mean your house is all electric, water heater and furnace, then your plumber needs to pull permits probably. In order to get a meter installed, you will need an inspection. Your plumber should know all the details.
If you do need to change electrical, either moving a receptacle or adding for a blower, you can do it yourself. But if you have any doubt at all, how to do it, I suggest you hire a professional licensed electrician. Better safe than sorry, so don't play with fire.
Other than that, the rest is straight forward. You will need to do some framing, some drywall, some trim carpentry and painting or staining. The only other thing, most fireplaces need a noncombustible surface, even the ventless fireplaces, at the hearth, and surrounding the fireplace. It can be brick, stone, tile. Usually, I have seen people use tile. But I have seen brick or granite a few times.