This certainly can be the timing belt. The 3.4 has a belt and not a chain. If you have never changed it then that would be the place to start. To check it remove a valve cover and if the cam doesn't spin then the belt is broken and will have to be replaced. You may actually have additional issues since there is a possibility of bent valves due to the pistons hitting valves when the belt broke. This can be checked by doing a compression test on each cylinder once the belt is replaced. Unfortunately, I don't know how much this repair will cost.