So now our cockpit looks like this. The helm has been entirely removed and is slated for renovation.
Here is a photo of the bottom of the cockpit floor where the helm was attached. The plywood backer was full of dry rot and the metal plate was severely rusted. Luckily, the rotten wood was easy to scrape off and the rot didn't get into the core.
Here's the pile of rotten wood. This will get thrown away. All the other parts will be cleaned, reinstalled, greased and re-adjusted.
The bottom of the cockpit floor now looks like this. Other than working deep down under the cockpit, this job went rather smoothly.