While actually removing the gas fireplace insert isn’t overly complicated, properly disconnecting and capping the gas line is critical. For this reason, most people hire a professional to handle the work on the gas line or take care of the entire process to remove the gas fireplace insert.  However, here is a basic overview of the process to remove a gas fireplace insert: First, shut off the gas supply. Next, remove the trim pieces around the insert. At this point, you can unscrew the gas supply line from the insert. Gently free the insert from the wall or masonry—this step will often require a second set of helping hands. Finally, cap the gas line and test it to ensure there are no leaks.