I "winterize" my Samsung RF-197 (similar to the R-18 model) by driving farther south until the average temps are in the 70's.
Seriously, the ice cubes left in the tray are nothing to worry about as they are frozen anyway. You have to clear the water supply line and water solenoid at the rear of the fridge. How to best accomplish that is up to you.
You can try air pressure and blow them out, disconnect and drain them, or pump the "RV Pink Stuff" through the water supply lines. In the spring just clear the antifreeze by running the ice maker until the ice cubes are clear of any leftover antifreeze.
Dr4Film ----- Richard