91 chevy Silverado key wont turn?

Ok my vehicle just all the sudden starting smoking bad and so i was looking under the dash to see where the sizzling was coming from but coudnt find anything so i hooked the battery back up, and went to see if i could start vehicle and My key wont turn backwards or fowards Any ideas? What would cause the smoke? I went and bought an ignition tumbler but havent put in yet Becouse i have no idea how too, so before i start doing it thought i would ask if anyone would have a good idea for this problem Thanks.