hi guys my p38 2.5 diesel Bmw engined car pumps black smoke out on start up and under hard acceleration so I’m thinking valve stem oil seals my question to yous is how difficult is this to do I’m a guy who can change starters alternater air suspension bags struts springs brake pads but by no stretch of the imagination could I say I’m a mechanic I love messing with my rangy and when I do a job and it starts again I’m on cloud 9 so guys is it something I could do or does it go into garage thanks in advance. Bob