Almost all open bath RSU and USD forks assemble exactly the way described above. You can use a impact to remove the bolt holding the damper to the lower tube. For reassembly, if it spins you can put everything back together without oil to use spring pressure to stop the damper from spinning. You can also use a holder tool, or something wooden or plastic to hold it or even use an impact again at low psi if you know the torque it's generating. Fork oil in an open bath fork should be set by oil height and that is always with the fork compressed. The spring seat,washers,spacers and spring are left out while doing this.