Enjoy The Ride
THE N54 --- Well actually Most all modern day BMW's are NOT for the average JOE. I love the car and actually enjoy maintaining the basics myself. My 335i is CPO and it has really paid to have bought her that way. As far as cost go --
I do follow the "old school MM schedule" -- but I do change the oil every 5k with the cheapest LL01 oil I can find - but do try to stick with the same brand by buying in quantity. I like OEM filters both oil and air. Again I like OEM for the MTranny oil -- changed at 50K. I am looking at changing the diff oil but the lack of a drain plug does bite. SO -- don't look at maint as a burden -- I love the prospect of buying stuff on Tischer / ECS / Turnner / BAVAUTO. My new front brake set-up from ECS is on the way and I can't wait till I hear the squeal of the UPS man.
SO -- LEARN TO LOVE THIS CAR AND THIS TYPE OF STUFF OR THE WORLD OF BMW MAY JUST NOT BE FOR YOU.