OK, $55k + $7k = $62k. Is this plane worth $62K to you? I may be totally out of touch with the current market, but I think the shock discs have already been factored into the price. Now it may be that all the awesome goodies this plane has are not important to you and all you really want is a good, clean stock M20C, in which case pass on this one and keep looking. As someone who has actually paid for upgrades, I think this plane is one heck of a deal and the turbo makes it pretty unique! Don't be surprised if the seller doesn't budge on the price. I wouldn't.
As to the airworthiness of the discs, I'm sure they're just fine to fly on. My plane has the original discs on the nose from 1966 and they pass inspection every year. They're rubber doughnuts and they're dirt simple. If one of them were to suddenly rupture into tiny pieces (very unlikely as they will fail more gradual with visible cracking first), what's the worst that could happen? One wing, or the nose is lower to the ground. Kind of like a Cherokee with a flat Oleo strut. Not the end of the world.
If it were me and the only thing the pre buy turns up is these old discs, I'd pay the man and keep flying the plane as is. I would then plan on doing the disc upgrade at the next annual. Maybe start with the nose gear first as it is probably the most critical due to prop clearence issues. Then maybe next annual, plan for the mains.