Looking at buying 85 nissan king cab everything looks good but ac may need refrigerant may need a recharge.assuming for air conditioning?is that bad and or expensive?

If you try to recharge the A/C using the old R-12 refrigerant it would be expensive because you would have to take it to a professional to have it done, but they do sell do it yourself kits to convert the old R-12 to the new R-134a. Walmart I believe sells the kits and probably any auto parts store. Assuming there is nothing wrong with the A/C unit. You will need to have a professional evacuate the old R-12 refrigerant first because R-12 and R-134a don't mix and it is illegal to vent it into the atmosphere.