Your oil will go black very soon after a change that’s nornal, I put mobil 1 10-30w in mine , next change at 44k will go for 5-40w heavier oil as temps are real hot out here, always fully synthetic, injector cleaner like the previous post said, redex or stp stuff. That should take care of the fuel filter that has been mentioned on many posts should last a very long time if you use good quality fuel, oil filter is the easiest in the engine bay to change, now air filter I have no idea but need to find out, you do have to take off the engine cover front end pops out if you lift it, and as you reach say 30-40degree slant pull it towards you as the rear end does not lift out vertically but comes off if you pull it (there are 2 hex screws at the end of the engine cover that do not need to be removed just loosened and they are tricky to get to, and number of other 6 I think that need to come out before you attempt the lifting up and pulling) but that is all I know.

Black smoke? I would add the fuel line cleaners etc etc and take the x on a nice run, check your coolant level for sure!!!!! At the 50/50 mix get the bmw stuff, and let me know if you find out how to get the air filter out please…enjoy