Actually, if the dryer was installed correctly, you shouldn't have to disconnect the gas line. It should have a coated flexible supply line ( usually yellow)connecting the dryer to the stub with a shut-off valve. This is so during installation you can have the dryer several feet out from the wall, make the hook-ups for gas and vent, turn on the valve, plug it in, then slide the appliance into place.
So, you should be able to pull the dryer out several feet, at least far enough tto climb over it to get at the supply lines and vents. If not, then there is something screwy with the installation.