On the 128 the oil drain bolt in mounted vertically. SO when you remove the drain plug the oil just shoots downward, into your catch pan.
On the N54 engine it is mounted at near 90' angle. Sow ehn you remove the drain plug the oil will shoot a little sideways. More so IF your can is not level when jacked up from one side! Ask me how I know this! lol So... I just put some old oil rags up in that access pannel to stop any oil getting up inside the belly pan. No big deal.
Asking what kind of oil is like getting into religion or politics. Don't ask. What ever oil you do use it MUST say... "BMW Long Life 1" or BMW LL-1"
So far the only oils sold in the usa that meet this are: Mobil-1's 0w40 LL1 (black bottle logo) and the Castrol oil that you can buy thru any BMW dealer.
I would also use a BMW original oil filter. I bought an OEM Mahle one, but the BMW filter looked like it was made better. IF someone can tell me(PM) how to post pics here... I can show you the pics side by side.
When you do your own oil change I would also have a clean turkey baster handy to suck the old oil out of the filter housing - bc there is alot of old oil left in there.
Btw... when I changed my oil I just dumped sven quarts of oil in there. I thin the reason why some people are getting a "full" reading on their electronic dipstick is teh same reason why you can fill up your tank NEARLY full, but the gauge still reads full. There must be some sort of "buffer" on that dip stick gauge, like there is on a fuel gauge sending unit.
Good Luck,
David