Its all good! I actually had forgotten I had a dealer replace ( I assume drain only) the transmission at 55K-6 years ago. Its now got 105K. But I already had 6 qts of new Nissan Matic S so what the heck. The pan also appeared to have a lot of rust so I decided to drop it & replace. The pan bolts were a little tough to get off due to rust. Luckily I happened to have one of those threaded type sockets that fit, so it tightens down as you turn it. As it turned out, I think the pan had quite a bit of life left, but now I'm good forever.
The old pan had a little bit of sludge on the bottom, but absolutely no metal bits. The screen looked perfect so I didnt touch it. I pulled off the magnets & cleaned them. The old fluid was pink, clean & no smell - perfect.
I added in 4 1/2 qts, no leaks at the new pan, sweet!