Yep they're the ones!
General rule, undo the filler before the drain - because if the filler doesn't come undone you don't have a dead car with its oil drained!
You'll need a square drive key. Amazon do a set for peanuts; PRIME too.
Washers are compression washers so best to get a pair. Already compressed washers never quite seal again.
Hopefully the square drive on the drain plug wasn't as butchered as mine.
I found filling was made easier with a two foot long tube with a funnel and fill from above.... slowly! I cheated and had a spare 90' elbow so used that to go into the 'box.
I spent hours and hours researching gearbox oil. Haynes is full of lies. There are pages of threads on here about it. Opinions included that Volvo modified the Renault boxes, some oils are not compatible with the bronze syncro rings...... plus many many more scare stories. The safe bet is the genuine Volvo oil. This is the one that comes in a bottle the exact capacity of the 'box itself. Volvo still sell it; Cambridge Volvo gave me a price to make your eyes water only the other week. I didn't want to pay that and used Millers TRX SYNTH 75w80. I am in no way telling you to do the same but my reasoning was :
• Its dual purpose GL4/GL5; a lot of the threads argued it should be one or the other; well this is both so happy days.
• Millers list it for the 480 in their online parts catalogue
• Its available from OPIE OILS
• Its cheaper than the Volvo stuff
• Its also listed for the Renault 21 Turbo which is a much greater animal (that torque steered all over the place!)
I cant say its good oil because the car is laid up, so if the gearbox explodes I take it back
Given that the drain plug was so mullered, I'm not convinced the previous garage invested so many hours into oil research. That may be evident by the amount of sparkly gold swarf that came out. Any ordinary garage would slap any old stuff in
Lastly, if you fill the 'box up to the point of overflow on a set of car ramps, when you lower the vehicle it will be slightly overfilled. Drop it to the deck, get the car level and fill from above is my advice
Good luck!