FWIW: a bit long, but,
Wouldn't it be a good idea to drive it for, oh, 100 miles or so, to get all the seals "resealed", and get all the gunk that may have settled in the cooler, nooks and crannies in the tansmission into suspension, and then do the flush?.
A really well respected, trans shop--one that does not have to advertise, recently doubled in size, and is always busy- and I have personally used, does not recommend changing the fluid on older vehicles when there's a problem. I had an escort's auto trans act up, and after they partially changed the fluid, it got worse. They put the old fluid in (following their own policy, they saved the old stuff) and the trans came back to it's cantacerous, but working self. I got another 840 miles out of it before I could sell it. Maybe luck, maybe a one-off occurance, but, it kinda goes with the if it's not broke don't touch it thinking.
I would, however, pull the dipstick and look really closely for signs of pitting/rust on the dip stick. If it was stored in a damp area or one with large heat cycles, then I'd change the fluid for a period-correct fluids; do check for potential compatability problems. I know on some manuals, where there can be huge compatability problems with current, new fluids and older trannys. Something to think about.
Continue debating.
