If you have the G54b, it has a timing chain and not a belt, so don't change it. Change the belts, hoses, fuel filter, all fluids, and check the brakes. As Sleeps says, do the tune up and run a good fuel system cleaner through it, like redline synthetic fuel injection cleaner - works great on all vehicles. After you get it running right, start adding Sta-bil marine ethanol gas treatment - eliminates the problems ethanol causes with older vehicles.