Generic buying advice - secure your own financing beforehand then ask the dealer if they can beat it. If they can, do so, if not, use your own financing. Do as much of the deal via email if possible, ask for an itemized out the door price. If they won’t give one, move on, that’s a sign they want to screw around with you.
Specific to Fiats, they’re sensitive to maintenance. Ask for any records they can provide, though they probably won’t have them (unless it’s a dealer and the vehicle was serviced by dealerships, which they’ll be able to look up).