D4D transmission flush

My newly purchased D4D sat for several years before I brought it home. As soon as I got it home, I checked the fluids and noticed that the transmission oil was milky white. When I drain this oil, is there anything that you would recommend to run thru it to clean the transmission before adding the new oil? Also, what kind of oil should I add back into it? I've seen several articles where people run SAE30, but I want to make sure I run the right stuff. One more thing...is there a filter in this transmission, and if so, where might it be located?

Thanks for your time.

1974 D4D 82J4040

D4D transmission flush