My main concern with the proposed maintenance/renovation of your rudder is that there may be prexisting damage from before the boat was hauled and because of the long dryout.
It is hard to say what should be done without seeing the setup. Maybe you could post some pictures.
Before you do anything check the steering
. Does it work smoothly as the rudder swings from side to side? Is there any binding or unexpected friction?
Then check the emergency steering
. Is it there? Does it fit? Can you use it to "steer" the boat?
Now consider if it is desirable to remove the rudder from the boat completely.
Can all shafts, pins, pintles, hinges, fittings etc. be removed?
The best result may be obtained by removing them and replacing all bolts pins etc. with new hardware
Now if you have a rudder that is stripped of all fittings consider sanding
it back to bare wood. Don't forget that old antifouling (paricularly as dust) can be very toxic so take all necessary precautions (gloves, overalls, quality dustmask etc.) here.
There are many ways of preparing woood for immersion by to my mind the WEST System has stood the test of time. My preference would be to leave the rudder out in the hot sun for most of one day, maybe turning it so it gets good and warm and dry, then coating it with straight WEST Epoxy as it cools so the cooling
rudder sucks the epoxy into the wood. Good dry wood can take many (3+) coats of epoxy.
After the epoxy has set sand the rudder again and fill all gouges, cracks etc. with WEST System filler.
When this sets fill and sand again as necesary and apply two coats of WEST Epoxy with white pigment added.
Sand this lightly when set and finish to match the rest of your boat.
Reassemble and check for correct functioning. Don't forget to replace any corroded zincs.