A lot of litres required. I wanted to do it on mine garages were quoting £500 on its own due to the cost of the fluid.
In US some people are excessive they drain, refill, drive it, drain and refill again. I think drain and refill is enough even though all the oil doesnt drain out. Itll be dominated by new oil and the newer magnets will get any metallic shavings left in the gearbox.
Keith has the right idea. Im sure hed do it for half the 500 hehe.