I have a 2001 5.9 SLT with @73,000 miles on it. It has never been used to tow - has had oil changes every 3,000 miles (and all other maintenance at recommened intervals.) Its using about 1 quart of oil every 2,000 miles. Should I be concerned?

Check the PCV valve and the intake manifold gasket.

If the engine is actually burning the oil through the rings or valve guides, a guidline for overhaul is 1 quart to 1K miles.