Chevy oil in coolant

Hello. We just purchased a 94 chev lumina 6cyl from a private owner to use a secondary vehicle. The car has sat for 4 months before purchase from the owner, she claimed it ran good no probs other than needing a brake job. We towed it to our mechanic for brake line repair and new brakes. He was checking things out and found some oil under the rad. Cap. He suspects either a blown head gasket or intake gasket. He is checking further what the prob could be. He just says there is a little bit of oil in the coolant. He also said if it is the head he doesn't want to tear into it, and we cant afford that costly of a repair. Would you guys have any suggestions to avoid a costly fix if that's even the prob? Thanks, Dave in Mt. Pleasant, Pa.