It is either time for a oil and filter change or the engine is low on oil.
Collapsed hydraulic lifter? - try a quart of mystery oil
need to know what engine size and year 3.5L 2006
There is no maintenance on the timing chain unless it breaks. No you don't change it.
A diagram for a 2001 Chevy impala 3.4L engine & coil pack firing order
What year, what size engine? 2004-2008 Chevy impala
what engine do you have in your impala?
The thermostat is located in the housing at the engine end of the top radiator hose.
Any engine that the 03 Impala came with takes 4.5 qts.
The Chevy Impala 2007 camshaft 3.5 is located within the engine area.
Loosen the 2 dog bones on the front of the engine and pull the motor forward to get to the back plugs.
antifreeze lines
Of course you do not have to remove the engine. Take the car to a professional for this repair. Your question indicates that you do not have the knowledge or skill to perform this repair.