To the OP, Papa O. Be aware that the comments here are concerning 2 different Sprinter models. The T1N 2002 thru 06 here in the USA, and the NCV3, 2007 on up. The T1N is a way less complicated vehicle. Has a 5cyl inline engine that can basically burn any kind of diesel fuel and use virtually any kind of diesel motor oil, is a VERY reliable and time proven robust engine. The T1N's major issues seem to have been the turbo resonator which is an easy and cheap replacement item when needed and rust around the windshield, bottom of the sliding doors etc.
Now the NCV3 is a whole different animal. The engine has all kinds of emission related items, as do all diesels nowadays, that are giving some folks regular problems. The engine itself is a very reliable motor with few issues you ever hear about. It also takes a specific type of oil, (low ash), that must be used to protect the diesel particulate filter (DPF), and must use low sulphur diesel fuel. The electronics are more complicated too. We've had some programming issues with the HVAC controls also on our 2013 van which I made the 80 mile round trip to the dealer to get fixed.
Like I had mentioned earlier, alot of folks have no problems with their Sprinters, and some do, and when they do it's the pits to get fixed sometimes. Be aware of where your closest Sprinter dealer is, Mercedes or Freightliner, as they both can do the warranty work