Bought a 2003 406 HDi two weeks ago with 91 792 on the clock belt never changed, I changed the belt, tensioner, jockey wheel and water pump within the first 200 miles of owning it. If the belt goes the car's not worth keeping. Also don't pay out twice, change the water pump at the same time. Don't take a chance if the belt gives out the engine is scrap, the scrap man will glady take it off your hands,.
Belt change on mine (don't know yours)
72 000 Ardious conditions
Continuuous door-to-door use
Town use (e.g. Taxi)
Repeated short journeys, with the engine cold in low temperatures
96 000 normal use (e.g. mostly motorway)
I got the kit and bought the pump seperately at the same time, kit with pump included cost a lot more, hunt around.
Hope this is some help, don't mess about, change it.
Chris, March 2012