This is a rant, with a warning to all you self proclaimed handy people out there. Whether you do this for as living, or as a weekend warrior you need to know the truth about gas fireplaces. First of all, gas fireplaces are a decorative, convenience item much like the washing machine is to the knuckle buster, or the automobile is to the shoe leather express. The difference between the former and the latter is that an argument can be made for their necessity. The gas fireplace is entirely frivolous and makes about as much sense as a screen door on a submarine. This is my opinion based on nearly two decades of installing and servicing these appliances. If you're the user, and actually enjoy them, no offense intended. I have a wood burning one that gets precious little use because I'm too tired to stoke the fire.
The reason for the warning is that fireplaces are a whole different animal than a furnace, water heater, or any other appliance that burns fuel and has a pilot. This pilot is usually difficult to service and clean because of the decorative nature, function takes a back seat to form. It also means that servicing gas connections are a pain because there's precious little room to swing a wrench, screwdriver, or any other tool needed.
To be fair, there aren't really a whole lot of issues that come up with the appliance as a whole. Most are simple and fairly durable and I've seen some of the old gas log sets work for decades with little or maintenance.
The main problem with a gas fireplace is the pilot burner. It's not very accessible, the heat has usually done a number making the parts difficult to get off. Even if it has a hot surface ignitor like a furnace does, the ones sicked on me usually take more than an hour to replace. 90 percent of all their issues stem from the pilot and these can include the thermopile, thermocouple, or the burner itself getting fouled. I'm going to give you the most valuable tip in the world for servicing these fire breathing monsters that you'll want to pay me the first time this comes up.
When getting the pilot burner out, common sense is that you need to remove the tubing with a 7/16 wrench from the burner. This means unscrewing the tubing (1/8 inch) from the burner and you would be wrong. See, the tubing is usually secured inside the nut in such a way that if you spin the nut, you break the tubing. You have to hold the nut stationary and unscrew the burner or remove said tubing from the gas control, thread it through and then unscrew it carefully from the burner. Common sense doesn't apply to fireplaces, but try telling that to the irate customer who's fireplace you put out of commission. I had a customer and her husband get really ugly with me and blamed me for everything short of the world ending. People love their fireplaces more than life itself, it seems. Again, spin the burner, not the nut on these lest evil befall you. Maranatha!