[fintstone]

The vent is so you can put a fan under there to blow out heated air. If you take that panel off, there may be a manufacturer plate and model number under there where you can get more details.

Your plumbing is likely/typical for a gas log starter...but it will work fine with a gas log.

You can probably use any small gas log rated for a prefab fireplace (that will physically fit). You will probably want a vent-free one. You can use one of those in a vented or vent-free install. It is good to fill the hole so they don't burn wood (cheap pine will creosote it up and it will need cleaning and be a fire hazard). The wire screen is enough unless you have some odd code where you live. Gas does not have the flying ember problem. Most renters will only use it once or twice and decide it is too much effort.