Regarding ATF fluid I would go with the Redline D4. Thanx Dave he posted here on board sometime ago how good is this oil and my brand new tranny is currently with the Redline d4.
Do not use Mobil ATF, good brand but looks like it does not fit/work good for our old tranny.
Also do not use OE MB fluid it is not suitable for our tranny as well. The good dealer will tell you that the bad (stupid) will put it in your tranny.
Somebody uses Valvoline but I would not do that cuz it sounds cheap and not trustworthy.
How is your R (reverse) on the transmission ? usually it gets bad at this mileage.
Never heard about Castol ATF but it should be good if Gerry approved that otherwise you can always charge him for failure of your tranny
At 200 000 you are looking at lots maintenance if you really want to bring it back to good shape Do not think I am saying it is high mileage that is why it needs lots of repairs. Basically all cars with 100 000+ at this time due to age need lots of attention to be in a great shape. There is also famous "Gerry's rule of 5K" which is really true too.