1. First a transmission oil change should be about $60-80 max. Anymore and you are getting gouged.
2. The manual states to have the oil changed at 70,000 miles or so. Why would the dealer contradict the GM manual?
I find their response really suspect and would get a transmission fluid change... somewhere else.
I bet it is because they want to push their trans fluid power flush machine instead of doing it the proper way...I have received the coupon mailer from my dealer and they mentioned this as an improvement to doing things the old fashioned (correct) way...
Dealerships often follow their own path rather than your owner's manual for service intervals...
What they are referring to is if fluid hasn't been changed for over 100,000 miles, it is so dirty that sludge will clog some valve during the flush and better not to touch it. But I don't see much sense in replacing fluid without changing the filter. The only additional cost would be the filter cost and the pan gasket.
This topic has been debated for many years and there is no real correct answer that anyone can back up with facts.
I changed the oil on the GL at 110k miles, drained all the oil and changed the filter, the 2-1 shift clunk I had went away and all is good so if it were me I would dump the oil, change filter and call it good. Now that said you cant change all the oil unless you have a drain in the torque converter (the GL does) but you will get most of it. The MB service manual says change at 40k and then never again.
People think of the service advisor (also called a service writer) as a mechanic but basically they are salesmen. They're often paid on commission. That means that the more work they convince you that your car needs, the more money that puts in their pockets. All you are to the dealer is money in the bank. Its your vehicle, demand they do what you want them to do, not what they want to do.