I don't know what to do
 

2005 chevy impala 8.3 v6 160,000 miles
Ok I tried to help a buddy out to change my oil to get him some extra cash I ran the car for about 2-3 months and it started running bad so I pulled the plugs and they have oil on them so I called my buddy up and ask what kind of oil he put he said 10w 50.i don't know what to do should I try to fix the car are sell it as is I payed 3500 for it.

Clean the plugs and see if it runs any better and how long it takes them to get oily again. If you really like the car and everything else is in good shape then it is worth putting some money into. If it runs real bad, you can't get your money back when you sell it.