If it's only a small hole, it can be filled with some fibreglass or better, epoxy-based putty without removing it .
Once, our boat was accidentally grounded and I decided to take off the swing keel for inspection. I placed a strong plank of wood on the trailer in front of the keel. then I lifted the boat with a hydraulic car jack (the one with wheels) placed on the plank. Mind you, I placed a piece of wood and a piece of expanded polystyrene on the jack to protect the hull and spread the load on a bigger surface area. The keel bracket is held only by the bolt accessible from inside. Then when it is lowered a few inches, the pin of the centreboard can be removed so that the board could be taken out sideways.(mind your fingers) The most difficult part is to put it back in but you will need someone else to help you.
A better method would be if you could rig a frame and remove the boat from the trailer.
