won't start and smells of gas

A smell of gasoline from the engine oil could be a sign the engine has been running rich resulting in engine oil dilution. I wonder if anything has come undone after the tune up, like a connector that got disturbed or has become loose. If that's got a 5.7 V8 its got an electric fuel pump in the fuel tank. If the fuel pump was mechanical mounted on the engine I would be afraid the diaphragm ruptured an was letting fuel into the crankcase. Crank angle or cam angle sensor or many other issues could cause loss of spark/fuel delivery but it is too hard to speculate without seeing the vehicle first hand and be able to do some tests.