If I remember right the 300 swing arm also takes a 17mm allen to remove the swing arm bolts, but not a 100% sure. Being an older bike you may not be able to break them loose from rust or maybe even damage the treads in the frame getting them out.
The u-joint can be changed without taken the swing arm off. You can unbolt the rear end assem from the swing arm as a unit and roll it out of the way on the tires. Just slide the driveshalf and joint out the rear of the swing arm tube. Loosen the swing arm boot clamp that hooks to the engine to help push off the old joint and line up the new one on install.
The u-joint can be changed without taken the swing arm off. You can unbolt the rear end assem from the swing arm as a unit and roll it out of the way on the tires. Just slide the driveshalf and joint out the rear of the swing arm tube. Loosen the swing arm boot clamp that hooks to the engine to help push off the old joint and line up the new one on install.
