Oil in the spark plugs question?

i am looking at buying this seabring for cheap it has 130,000 miles but it has a few problems but the one that i am worried about the most is the oil in the spark plugs the guy tells me that its only valve cover gaskets thats causing the problem we took it for a test drive it runs run and drive alright beside it has the jerky misfire to it .....after i drove it i looked at the exhaust no smoke ....seems to me it could be a fixer upper idk what to do ... idk think it could be rings coz smoke would be coming out of the exhaust right? what should i do