Hi Alan
That's the one! There's a similar one underneath the box if you need to drain it.
It's best to use a special square spanner on these - they're depressingly easy to chew up.
For filling the box, I find it easiest to remove the undertray and use a container with a flexible spout. You can then squeeze the oil into the box - much better than approaching it from above, as you don't risk losing the top/spout of the container.