I should check the weight / pressure required...any ideas on how to do that simply?
If you steer easily by hand , that is all you need.
If its arm wrenching Victory At Sea , all the time hyd would be better.
It is probable that the boat was built with OTS parts , like an Edison chain steering although years ago good boat builders made much of there own parts.
Hiding the unit behind a cabinet would require replacing the chain drive with one that accepted 2 chains , or simply making the drive chain longer so the AP can get to operate it.
The std sail AP unit would be visible behind the wheel , but its just a small motor and a black belt.
If this was 30 years ago I would suggest a Wood Freeman chain drive unit , but sadly simple has been replaced with unrepairable.
KISS is always best.