Can anyone tell me how many quarts I need to do a pan drop and filter and gasket swap and refill on a 04 320?

I think they usually recommend 4-5 (do a search on here it has been mentioned) for just a pan drop but I would recommend if you are doing that much might as well do a full flush as well which would require 12-14 depending on how dirty your fluid is. When I did my car I believe it took 12 but I bought extra to top off if needed.
Make sure you get the dipstick so you can measure the fluid as just a little bit to much or to little makes them behave horribly.

Hello, My E350 slips into park at low speeds. Dealer unable to replicate issue and not sure about the problem. Any ideas? Could it be a transmission issue?