I purchased the extended warranty for my 2000 ML320 (62K miles) and have suffered with hard shifting which the local dealer says is a control unit (item on order).

To replace the control unit, do they need to drain the fluid?

I know the fluid is lifetime, but I'm thinking of having them change the fluid and filter while they have it on the lift. If the fluid is changed during the repair then I can save my $$ for other stuff that isn't covered. (Those plastic trim bits cost more than chrome for the bike?!?)

Thanks in advance.
Rob