They are no different than other vehicles in regard to performing maintenance. You would be fine!
The 3.0i wont get much better in mpg than those 4.4i. Shop for one with sport pkg and maintenance history. Have a PPI done and base your negotiation on it. GL.
01 Anthracite 525i Sport, 03 DINAN 540i M-Sport, 06 DINAN E53 4.8iS, 90 Straman Z32TT,
01 E53 3.0i and 91 Z32TT (Gone, but not forgotten)