It would help if you could see the paperwork for the job that was done. If it lists the seals and a Vibration Damper (also sometimes called a Harmonic Damper) then it would be fair to say the whole job has been done properly.
Also if you start the engine, let it idle and look at the crank pulley/damper, if it's wobbling about like a car on the fairground waltzer there's a fair chance it was only the seals.
If it looks bright, shiny and new and runs as true as can be, there's a very good chance it was all done.
If in doubt, blow it out. There's usually more than one Volvo available for sale at any given time.
