Mirror vibration or slap in a Hassie is one of the most common causes of lack of image sharpness. If the damper is bad, how do you know something else doesn't need attention on that body?
This kind of begs the question of how are you going to decide whether or not to keep it if it's not working at it's maximum performance level? If you like it, keep it and get it CLA'd at a reputable shop. I'd do that first. They'll go through it and fix what's necessary to bring it back to spec (or as close as possible). When you get it back, THEN test it. ;>) and odds are you'll be really pleased with its performance and results.
Take it light ;>)