There is no excuse for taking your money and not producing or responding. It takes less than a minute to respond to an email. Get in your vehicle and drive to his house.
Raymarine claims that there are no user serviceable parts inside.
Raymarine Classic Multifunction Displays require a SeaTalk1 to SeaTalkng converter to connect an RS130.
Turn the wheel from stop to stop and count the turns. Divide that in half and turn the wheel that many turns from one of the stops. Then eyeball the rudder.