Oil every 6-7k miles or once per year. Full fluids once every other year. Check the manual for extra bits like belts, filters, etc etc. The cost of an oil change can be $400-1000 depending on where you go and the full fluids/belts change can be as high at $2400 at a dealer. The clutch will need to be replaced every once in a while depending on your driving style, you should have then change not just he clutch but also all the bearings etc etc and it can run you up to $6000. Some have paid $3k, but I think that this lower price is just for the clutch plate replacement - not recommended.
2006 GranSport, Maserati Corse Victory #65, Bianco Fuji
2006 Quattroporte Sport GT, Nero Carbonio Metallic