HI
$800.00 isn't enough to fix it... especially from a dealer.. go to another shop.. did they say how they checked it?? When a dealer says what they did to you I would never recommend them to anybody..
It is most likely Valve cover gasket (s) (you don't say if its a 4,6 or 8 cylinder) timing chain cover gasket, oil pan gasket, mail seal's ( that is very expensive), oil sending unit.
good luck
tim