funky problems

just purchased a 98 jimmy for my sons first car. old owner just replaced the fuel pump. the key would not turn so i replaced the key and lock assembly last night. the engine now turns over just fine. all electrical compnents seem to work...except the headlights. have ac/radio/turn signals etc. when i turn the key off and remove it the odometer led stays on as well as the inside lights. ..as stated, the engine turns over but does not sound like it is getting fire...so i'm assuming some saftey switch is stopping the coil from working....any ideas would be greatly appreicated....thanks....peace