The crash of my L39 prototype is a good opportunity to show how easy it is to repair 3d printed P5 parts. Since the entire rear is intact, only the front fuselage is reprinted.
Since you can't cut the parts exactly at the glue joint, you keep the base plate of the broken part and only remove the gyroid infill. When removing the interconnects you see why I recommend in the manuals not to glue them. Now you can just pull them out with pliers and reuse them. Cut off all the infill and the outer wall and sand the surface smooth.
Since the first layers of the old part still need to stay on, you'll need to print the new part shorter by this distance. To do this, simply set the Z value in the slicer to - 0.8 mm. The part is then offset 0.8 mm downwards and the total length is correct again after assembly.
Now simply position and glue the new part as usual. You will hardly see that anything has been exchanged here.