My sister has a 2003 buick century approx. 140k miles. The low oil light had been on forever amd finally Friday night the car died. She poured a gallon of oil into it and it started back up. Ever since there has been a loud ticking noise in the engine and she says it smelled like something was burning. Our machanic brother suspects its the lifters.. my question is does this sound right (I'm sure it prolly is) and if so how manh lifters would she need to buy and how long/difficult is it to replace them?