Just did it with a friend a couple weeks ago to my 2001 330i- we used RedLine MTL for the tranny and since I am going to do some performance schools and Auto Crosses I plan to change both every 3 years. Used Mobile1 75W90 for the diff...
Got 2 hand pumps from AutoZone and got 2 gallon containers - well built washer fluid containers worked will. Get the car up on jacks and level, loosen the top bolt (not mandatory) and drain via the drain plug. Add the fluid to the clean containers and attach pumps. When done draining tighten the upper bolt (if loosened) and then pump fluid into the tranny and diff till it runs out of the fill hole.