I can't help with the boom, but I know that when removing the outer shaft, it is tight. When you tighten the bottom screws on the lower rotor head and the set screw on the retainer they leave marks on the shaft which make it very tough to get the shaft removed from the retainer and bearing. I put some light oil on the shaft and tapped on it until it came out. When I reinstalled it I sanded the screw marks with fine sandpaper to help with reassembly.