Valve job
 

I had a spark plug loose and it caused my engine to sputter and smell like flooded gas. Replace spark plugs and wirering note one spark plug was loose and my mechanic said that's probly whats causing the sputtering how much would it cost to repair and labor just a rough estament.so I will know when I take it to a

That depends on what engine is in it.
My 5.7 liter has 16 spark plugs, so it would be more expensive by far than a 6 cylinder which would take 6 plugs.
Also, some engines use more expensive plugs than others.