Hi if the engine burns oil all the time cold or hot then yes you will need piston rings.
a job like this will require the removal of the engine and disasemble the piston rings run for 350$ , a gascket set 375$ oil and fluids 55$ and the labor 14 hours times the labor cost the entire job depending in the labor cost $1,890.00
mechanic states my oil sending valve needs to be replaced. It was cleaned out of sludge once before.What is the cost of part and cost of labor?
the oil sending unit or valve is not going to stop the engine from smoking, are you sure this is what the mechanic referred to?
if the engine smokes all the time then you need is a ring job, this will cost you approximately with gaskets ring set and labor approximately $1,600.00