So generally i'm a clean fluids kind of guy...
I've heard from a few people that new fluid in an old transmission can cause failure... The best explanation for this that i heard was that new fluid, having stronger detergent properties than old fluid can attack the clutch materials in the old transmission.
I have an 85 300d i just purchased. it runs well, transmission seems to shift well (a bit of a hard shift when cold, but that seems normal) 143,000 miles. I have no idea when the fluid was last changed. It is pink on the dipstick. If this transmission pops the car is getting parted out... i'm a student, i can't do a transmission right now.
So should i risk fluid and a filter? I basically need this thing to last me about 2-3 years. 40,000 more miles maybe?

is there any preferred fluid for an old possibly neglected car such as this?