I used to own a saloon version of one of these cars and I have a few tips to pass on.
I drove it from new and covered a total of 190K miles in 13 years.
I serviced it myself after I found proffessional work sadly lacking
The engine is a 6 cylinder VW LT van engine, and you will find there are many who will shake their head and say it was a "bad" engine as it was known to fail with broken camshafts and cylinder head cracks.
In fact most of the failures can be put down to incorrect servicing. When VW says that you must change the oil at 6000 miles you must do it. I changed mine at 5000 to make the service interval easier to note. The engine, I believe, has little oil jets inside the cylinder block that sqirt oil on to the thrust side of the cylinders to lubricate and to cool them. If the oil gets thick and sludgey, these can block and cause the engine life to be reduced. If you acquire one of these engines (or any other for that matter), it is always a good plan to change the oil immediately and again 1000 miles later.
The tappets are a pain because they are individual shims that you have to change. I used to get away with swapping them around with some 7 or 8 spares and usually having to buy one or two. Garages have a big box of them that they swop to and from. As well as feeler gauges you will need a metric micrometer of caliper to measure the thickneses as the markings sometimes have rubbed off.
The body is really well made and did not have any rust on it when I sold it except a cross bracket under the radiator that I had to treat. I wish my present Mercedes was as rustproof.
The engine sound was always rattley from new, but quietens down a lot when warm.
I bought most of my bis from German and Swedish or Europarts as they were good and a lot cheaper. About 8 years ago I paid abot £20 each for Bosch injectors in the makers boxes.
The car had great acceleration, and I still miss it. regards, Ben