Gearbox and diff oil is easy, it won't have been done when the clutch was replaced as there's no real need unless you had a major service done ??
The interval is 3 years Iirc.
Gearbox/front diff, there's a drain plug on underside of the box, remove and drain, as for re filling you have to use the gearbox dip stick hole underneath the intercooler, a funnel and length of hose is easiest for this.
Rear diff there's a drain hole and a fill hole on the back of the diff as you look at it from behind, think they are 22/23mm plugs, undo the top one 1st to make sure it comes free, then undo the drain plug at bottom,
Refute drain plug, fill via the top hole until it starts to come out the pop the plug back in again
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