Noise? What noise? What does your dealer say the noise is? How many
miles on it?

If the engine doesn't seem as quiet as it used to, try 10W30 oil, or a
different brand if already using it. The dealer may be using 5W20.

If you have a 4 cylinder engine, it is an I-4, not a V4.

if it still runs fine, there's absolutely no reason to spend thousands
to replace it. What makes you think all those connections to wires,
hoses, other parts will be done right?

Engines get relatively few miles in Japan, if you did replace it, you
can probably get a cheap, low mileage engine that has been imported
from Japan. Search on the Internet. It's only worth it if you plan on
years more ownership.