Sorry arnie,
but I need to correct you on the degree of difficulty on the oil change on a 5hp30. They are easy in fact because all you need id a good length of plastic hose and a small funnel that fits the hose. The other end requires a piece of copper tube bent at about 90 degrees.
You just need to slip the tube into the filler (hose attached) which is in the pan and tip oil into the tube from a height greater than the tranny i.e from standing next to the car and pur in the specified amount till it overflows out the filler hole.
No dipsticks, no marks and you cannot overfill.
The ZF recommended oil was Shell (see ZF website) but Castrol has a product called Transmax (green) which is supplied to BMW as a "special BMW branded" oil.
There is the BMW story and the real story. Don't believe everything they tell you
cheers, hope it helps