The 156 1,9 JTD 16v uses a similar cam belt set as the petrol engined version. But check when ordering that its for your model.
The official live of the cam belt kit is 3 years and or 37500 miles what ever comes first. I believe that the diesel engine is less liable than the petrols as it doesn't run that many revs as the petrols. I don't think the diesels have cam variator.
Many of the service items needed for the 156 are often shared with the 147s.
I had a 156 2,0 TS MY 1998 until it was 12½ years and 135.000 miles old. I didn't have any real choking issues with it. None of the real expensive parts such as generator, steering pump, clutch, drive shafts, radiator needed changing. It had one exhaust, some parts in the front suspension, the wiper motor and connection and a battery once.