RATIONALE: Drugs used in chemotherapy, such as gemcitabine and cisplatin, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving chemotherapy before surgery may make the tumor smaller and reduce the amount of normal tissue that needs to be removed. Giving chemotherapy after surgery may kill any tumor cells that remain after surgery. It is not yet known whether giving chemotherapy before surgery is more effective than giving it after surgery in treating non-small cell lung cancer.