Yes, that's the one. Rasputin had one but when I changed the sump I had to remove the manifold, and that required the bracket to be removed, when it promptly fell apart.
It bolts to a triangular (from memory) bracket that is bolted through the two lower front bolts that hold the bell-housing on, so if you have nothing "bracket looking" hanging from the bell-housing, you'll need to rustle one up from somewhere.
Don't worry about heat build up with the under-tray. My old Stilo didn't have a tray when I bought it, and when I replaced it I didn't notice any difference whatsoever.
Any excess heat in the engine bay would transfer to the coolant, so you might get marginally more radiator fan action in the summer.. but if the car is moving, the bottom rear of the under-tray would act like a venturi anyway, so it will tend to suck air out.
If you have one of those cone filters a warmer engine bay might give you a bit less power... but if you have a cone filter you probably have a shield and a cold air feed too.. so no bother.
Where did you get your tray from? Is it a metal or a plastic one?
Ralf S.