the oil leak may NOT be a head gasket leak, specially if it is at the front cover seal area, which is very common. You can treat as the head gasket for price negotiation if you are really interested in the car.
However, the lumpy idle may be something as simple as a vacuum leak or it may be related to the head gasket.
Any records on the car? last service maintenance?
Records on these cars are very important, specially on older cars since repairs can become expensive real quick!