As long as you drop your working pressure down all the way to zero it shouldnt matter. But its doubtful you will get the working pressure exactly the same so may need to do an adjustment to the needle valve anyways.
Don't close the needle valve till it stops. It may ruin it. There's no need to close it anyway. It's more important to close the working pressure when changing the cylinder out.Ok. To be safe I'll close the needle valve. It's easy enough to set it back to where it was. Thx.