My 2002 4.6is has an engine noise at idle that sounds like the main bearing is going. Is this a possible problem on an '02 with 45k miles on it? Perhaps the old owner towed a too heavy load up a mountain?

What is the cost for a replacement engine in a 4.6is?

Is it possible to upgrade to a better engine if this one dies?

What is the life expectancy of a 4.6is engine?