Just remove it when it is not extended (I’m talking about the long springs that are on each rail of the door NOT the one mounted on the wall of the garage over the door). Remember it balances the weight of the door. So they will be “unloaded” when the door is raised - and once you take the springs off the ~300lb door will have no resistance. I’d highly recommend blocking it up so it cant be closed while you work. It could damage your door, opener or hurt anyone under it. Make sure you properly replace the safety wires as when the springs fail, they do so in a dramatic way and those wires prevent them from falling.