To change-or not to change
I could really use some sage advice from all you experienced Ford wrenches. I have recently become the proud fourth owner of a 1977 Mercury Marquis. The former owner held her as a garage queen, and thought it was enough to start her twice a year a pull her out annually for a new coat of wax. All the fluids need renewed as he said he didn't dive it so he never changed them. So to get to my question...the odometer is showing just over 55,000 miles which is supposed to be original (but who knows, in PA. the reading is exempt for vehicles over a certain age) I am sure the ATF has never been changed, would fellow forum members recommend doing so? The fluid when checked is no longer red in color (more brown and oily) and on the dipstick has been way overfilled. My older friend at work has warned me that if I get the fluid changed the higher pressure will dislodge sediment and gunk that has accumulated over the years and I will be replacing the transmission within a month. I have heard this before and even from trans. shops, and it has scared me out of doing it. I don't know who to believe, any imput you folks could provide would be appreciated.
P.S. The trans. is I think a C-6 and uses type "F" fluid. One of the former owners had a trailer hitch on it and it currently shifts fine.