Hello PhilCal,
You really don't need to undo those other two originally square headed plugs as that just makes a mess on the machine.
Just open the filler and place with your other hand an empty Ice Cream container directly under the filler neck while tilting the machine backwards. You can lay it all the way back and thus all the oil will come out.
When refilling it just fill it with new oil up to the bottom of the visible casting of the filler neck.
That's it !
Cheers,
BB
