you have two questions.
1. When moving the gas line it must be pressure tested and should be inspected by the utility or the Jurisdiction Having Authority.(City, county etc.) The gas valve is normally located outside of the firebox to eliminate any fire danger due to heating of the piping.
2. Gas fireplaces must have the vent damper locked in the open position to eliminate the posibility of Carbon Monoxide poisoning. this pretty well limits the us of the fireplace for wood. Also in order for the gas to be used and not put all the BTUs up the chimney you need to have a set of fireplace logs that serve to convert the BTUS into radiant heat that will go into the room this provides about a 50 to 60% efficiency.
Most gas fireplace inserts reconfigure the venting and the combustion air to get the operating efficiency up to the 75 to 80% range but completely eliminate the ability to use wood.
Hope this answers your questions.
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