2004 x5 help

[X5mjm]

I love my x5 with 86000 miles. Had it checked out by 2 BMW repairs. When I start it black smoke comes out. BMW scoped the engine and said 1 piston had low compression in the 80 range. The said I could use a new head gasket too. No oil leak but I consume way too much oil. Second thing is the car has been not starting once a week. It turns over and cranks but won't fire up. If it sits long enough it eventually starts. My mechanic said sounds like the fuel pump does not have enough pressure to get the car started? Other than that I love it. I can't see spending 1100 for the head gasket and 4500 for new rings. Does this make sense?