Choosing a filter

I'm going to be changing the filter in my tranny within the next few weeks (97 Riviera S / C) and am having trouble choosing the filter and fluid. I have no idea if the previous owners regularly serviced it or not, but when checking the fluid it doesn't seem to be bad. No slipping or hard shifting either. I assume its the 4T65E-HD but most parts stores list a filter kit for the 4T65E as being a direct fit for my car. Are the filters the same in both? And then for the fluid. What would be safe to put in there not knowing what type of fluid it will be mixing with. Car has 200k+ on the dash.

Filters are the same. The pan gasket is reusable. I have been using this for fluid,

http://www.valvoline.com/our-products/automatic-transmission-products/maxlife-dex-merc-atf

My original transmission shifts perfectly at 166,000 miles

Thanks for the help.