possible new owner of 2jz s13

[at15]

Im new to the 240 world and looking at a 1991 with a 2jzge swap from a 94 supra. I talked to the guy and he said it has a slight miss sometimes, He said he changed the valve cover gaskets and dripped oil on something and it should go away or just change the spark plugs. Says its no big deal. What is he talking about? Also value wise is 5k on par?
here it is...http://greensboro.craigslist.org/cto/4959774064.html