W204 Estate Transmission fluids?

Hey Guys,

I hear mixed stories about servicing the transmission fluid.

I've had it since 50kms and I am not sure if the trans has ever been changed, it's at 80kms now and I have done oil every 10k's, however I have never seen the report of the trans being changed.

Should I do it, everyone says no the fluid is now so viscous that putting new fluid in it is suicide, should I change the fluid and filter but ask them to put the old fluid back in or do a full service?

It's not shifting slow or slipping, it's very smooth in S+ and Manual but I wanna keep it running good, should I not mess with it?

My gut tells me to leave it but I am big into preventive maintenance as this V8's are getting harder and harder to find these days and want to keep it running great.

Cheers.