I want to service the automatic transmission on my 1996 BMW 328i..

What is your question?

I understand the flushing the entire system will harm your transmission. Therefore, how many quarts of fluid can I expect to extract from removing the pans and drain plugs? Do I need to drain and refill multiple to make clean. Since Dexron III-Mercon is the lifetime fill, and no longer available, What fluid can I use that won't destroy my transmission?