Sorry to hear of your misfortune with your SAAB
I think I'm correct in saying that an 09 diesel engine will have a DPF (Diesel Particle Filter) in the exhaust, all diesel cars have these now.
These are prone to clogging up and causing a lot of problems if the car is only used for short start stop sort of journeys.
Vehicles fitted with DPF's need to have a regular longish run at cruising speed to let the filter regenerate, even if this is done they sometimes still cause problems and are expensive to replace.
Have a search on Google about them.
Not sure what
& filter service intervals the latest DCi's have but to look after the engine ignore any long service intervals and change the
& filter a lot sooner than they tell you. (every 9k or sooner)
The 2.0 DCi has a timing chain (instead of a belt) which needs no servicing so that will save on servicing costs unless it has problems.
The reviews I have seen on the new laguna seem quite good, but none of that means much unless you like and feel comfortable in the car.