Cables should probably be replaced. Both shifter and brake cables can be under considerable tension, brakes particularly in emergent situations and rusted cables are more likely to break. A broken brake cable can be a disaster. Broken shifter cable an annoyance. Look for stainless replacement cables. If the cables are rusted inside the housings, then probably the inside of the housing is rusted as well. Housings rarely fail however, they just increase shift resistance. A couple of chain cleanings will likely get rid of superficial rust, which is not unusual with chains. Steve