To Remove the Rudder
Loosen the wires on the quadrant. It's not necessary to undo completely. Chock under the rudder to stop it falling through. It's not necessary to excavate beneath the rudder, there is sufficient ground clearance. Remove collar, loosen quadrant. Remove keyway from under quadrant. (Use a metal chisel and a hammer and hit it very hard on the side of the keyway and the keyway will spring out. Do not be gentle!) Slide the rudder stock down through the bearings and remove. Refitting is the reverse of the above.
There are 2 bearings at the top and bottom of the rudder tube and it is generally considered a good idea to replace them once there is play in the rudder. If you hold the bottom of the rudder and there is latteral play (as opposed to vertical lifting) in the rudder then it's time to consider replacement. The rudder bearings are just a press fit into the rudder tube. They were originally made from Tufnell but modern replacement bearings are made out of hard plastic/nylon. They are usually supplied oversize externally and have to be lathe turned, filed or in desparation use an angle grinder to fit. To remove existing bearings, use a suitable drift to push out, or use a hacksaw blade carefully sawing through the bearing without scoring the tube surface. It's generally a good idea to replace the "lip seal" at the top of the rudder tube at the same time as replacing the bearings.
At the time of writing, only one supplier of spare bearings are known, Trafalgar Yachts