Ignition Key Stuck in Run Postion! HELP

i have a 1990 Chevy Suburban R1500 with the 350 TBI Engine. My Key is stuck in the run position...i have to disconnect the neg. end of the battery cable to stop it...and reconnect when i want to start it...ive tried all the little tricks to get a stuck key pulled back...but nothing works...does anyone have any suggestions? or can anyone tell me how to dismantle the steering column? help please!!