2007 buick lucerne

While sitting at a red light, i noticed faint white
smoke coming from Under the hood. I pulled into a
parking lot less than a block away, got out and
checked. There was a Heavy TRAIL of fluid, fluid all
over the drivers side of "motor", like a Burst
somewhere, when put back into gear, the car didnt
move (Transmission). Called for roadside and
towed home. Need possible "problem" idea, and
How Expensive should i expect?...PLEASE give me
hope and say "a HOSE"...