The only thing that I would worry about is the price difference you might have gotten if the car was not really a S90, but a 960 instead. The Volvo 960 and S90 are practically the exact same car, although in late 97-98 they did change the console area and seat design a little bit. You might want to confront the party who sold you the vehicle to refund the price difference because of the title and name mishap based on apparised values.
-Drew
-Drew